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-- Chapter 09 - Graphs, Trees, Hierarchies and Recursive Queries
--圖,樹,層次結構,遞歸查詢
---------------------------------------------------------------------
---------------------------------------------------------------------
-- Scenarios
---------------------------------------------------------------------
---------------------------------------------------------------------
-- Employees Organizational Chart 組織結構圖
---------------------------------------------------------------------
-- Listing 9-1: DDL & Sample Data for Employees
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Employees') IS NOT NULL
DROP TABLE dbo.Employees;
GO
CREATE TABLE dbo.Employees
(
empid INT NOT NULL PRIMARY KEY,
mgrid INT NULL REFERENCES dbo.Employees,
empname VARCHAR(25) NOT NULL,
salary MONEY NOT NULL,
CHECK (empid <> mgrid)
);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(1, NULL, 'David', $10000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(2, 1, 'Eitan', $7000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(3, 1, 'Ina', $7500.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(4, 2, 'Seraph', $5000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(5, 2, 'Jiru', $5500.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(6, 2, 'Steve', $4500.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(7, 3, 'Aaron', $5000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(8, 5, 'Lilach', $3500.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(9, 7, 'Rita', $3000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(10, 5, 'Sean', $3000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(11, 7, 'Gabriel', $3000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(12, 9, 'Emilia' , $2000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(13, 9, 'Michael', $2000.00);
INSERT INTO dbo.Employees(empid, mgrid, empname, salary)
VALUES(14, 9, 'Didi', $1500.00);
CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid);
GO
---------------------------------------------------------------------
-- Bill Of Materials (BOM) 物料
---------------------------------------------------------------------
-- Listing 9-2: DDL & Sample Data for Parts, BOM
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.BOM') IS NOT NULL
DROP TABLE dbo.BOM;
GO
IF OBJECT_ID('dbo.Parts') IS NOT NULL
DROP TABLE dbo.Parts;
GO
CREATE TABLE dbo.Parts
(
partid INT NOT NULL PRIMARY KEY,
partname VARCHAR(25) NOT NULL
);
INSERT INTO dbo.Parts(partid, partname) VALUES( 1, 'Black Tea');
INSERT INTO dbo.Parts(partid, partname) VALUES( 2, 'White Tea');
INSERT INTO dbo.Parts(partid, partname) VALUES( 3, 'Latte');
INSERT INTO dbo.Parts(partid, partname) VALUES( 4, 'Espresso');
INSERT INTO dbo.Parts(partid, partname) VALUES( 5, 'Double Espresso');
INSERT INTO dbo.Parts(partid, partname) VALUES( 6, 'Cup Cover');
INSERT INTO dbo.Parts(partid, partname) VALUES( 7, 'Regular Cup');
INSERT INTO dbo.Parts(partid, partname) VALUES( 8, 'Stirrer');
INSERT INTO dbo.Parts(partid, partname) VALUES( 9, 'Espresso Cup');
INSERT INTO dbo.Parts(partid, partname) VALUES(10, 'Tea Shot');
INSERT INTO dbo.Parts(partid, partname) VALUES(11, 'Milk');
INSERT INTO dbo.Parts(partid, partname) VALUES(12, 'Coffee Shot');
INSERT INTO dbo.Parts(partid, partname) VALUES(13, 'Tea Leaves');
INSERT INTO dbo.Parts(partid, partname) VALUES(14, 'Water');
INSERT INTO dbo.Parts(partid, partname) VALUES(15, 'Sugar Bag');
INSERT INTO dbo.Parts(partid, partname) VALUES(16, 'Ground Coffee');
INSERT INTO dbo.Parts(partid, partname) VALUES(17, 'Coffee Beans');
CREATE TABLE dbo.BOM
(
partid INT NOT NULL REFERENCES dbo.Parts,
assemblyid INT NULL REFERENCES dbo.Parts,
unit VARCHAR(3) NOT NULL,
qty DECIMAL(8, 2) NOT NULL,
UNIQUE(partid, assemblyid),
CHECK (partid <> assemblyid)
);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 1, NULL, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 2, NULL, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 3, NULL, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 4, NULL, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 5, NULL, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 6, 1, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 7, 1, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(10, 1, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(14, 1, 'mL', 230.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 6, 2, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 7, 2, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(10, 2, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(14, 2, 'mL', 205.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(11, 2, 'mL', 25.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 6, 3, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 7, 3, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(11, 3, 'mL', 225.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(12, 3, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 9, 4, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(12, 4, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES( 9, 5, 'EA', 1.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(12, 5, 'EA', 2.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(13, 10, 'g' , 5.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(14, 10, 'mL', 20.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(14, 12, 'mL', 20.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(16, 12, 'g' , 15.00);
INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)
VALUES(17, 16, 'g' , 15.00);
GO
---------------------------------------------------------------------
-- Road System 道路
---------------------------------------------------------------------
-- Listing 9-3: DDL & Sample Data for Cities, Roads
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Roads') IS NOT NULL
DROP TABLE dbo.Roads;
GO
IF OBJECT_ID('dbo.Cities') IS NOT NULL
DROP TABLE dbo.Cities;
GO
CREATE TABLE dbo.Cities
(
cityid CHAR(3) NOT NULL PRIMARY KEY,
city VARCHAR(30) NOT NULL,
region VARCHAR(30) NULL,
country VARCHAR(30) NOT NULL
);
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('ATL', 'Atlanta', 'GA', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('ORD', 'Chicago', 'IL', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('DEN', 'Denver', 'CO', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('IAH', 'Houston', 'TX', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('MCI', 'Kansas City', 'KS', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('LAX', 'Los Angeles', 'CA', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('MIA', 'Miami', 'FL', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('MSP', 'Minneapolis', 'MN', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('JFK', 'New York', 'NY', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('SEA', 'Seattle', 'WA', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('SFO', 'San Francisco', 'CA', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('ANC', 'Anchorage', 'AK', 'USA');
INSERT INTO dbo.Cities(cityid, city, region, country)
VALUES('FAI', 'Fairbanks', 'AK', 'USA');
CREATE TABLE dbo.Roads
(
city1 CHAR(3) NOT NULL REFERENCES dbo.Cities,
city2 CHAR(3) NOT NULL REFERENCES dbo.Cities,
distance INT NOT NULL,
PRIMARY KEY(city1, city2),
CHECK(city1 < city2),
CHECK(distance > 0)
);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ANC', 'FAI', 359);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'ORD', 715);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'IAH', 800);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'MCI', 805);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'MIA', 665);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'JFK', 865);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'IAH', 1120);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'MCI', 600);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'LAX', 1025);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'MSP', 915);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'SEA', 1335);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'SFO', 1270);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('IAH', 'MCI', 795);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('IAH', 'LAX', 1550);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('IAH', 'MIA', 1190);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('JFK', 'ORD', 795);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('LAX', 'SFO', 385);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MCI', 'ORD', 525);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MCI', 'MSP', 440);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MSP', 'ORD', 410);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MSP', 'SEA', 2015);
INSERT INTO dbo.Roads(city1, city2, distance) VALUES('SEA', 'SFO', 815);
GO
---------------------------------------------------------------------
-- Iterations/Recursion
---------------------------------------------------------------------
---------------------------------------------------------------------
-- Subordinates
---------------------------------------------------------------------
-- Listing 9-4: Creation Script for Function fn_subordinates1
---------------------------------------------------------------------
-- Function: fn_subordinates1, Descendants
--
-- Input : @root INT: Manager id
--
-- Output : @Subs Table: id and level of subordinates of
-- input manager (empid = @root) in all levels
--
-- Process : * Insert into @Subs row of input manager
-- * In a loop, while previous insert loaded more than 0 rows
-- insert into @Subs next level of subordinates
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.fn_subordinates1') IS NOT NULL
DROP FUNCTION dbo.fn_subordinates1;
GO
CREATE FUNCTION dbo.fn_subordinates1(@root AS INT) RETURNS @Subs Table
(
empid INT NOT NULL PRIMARY KEY NONCLUSTERED,
lvl INT NOT NULL,
UNIQUE CLUSTERED(lvl, empid) -- Index will be used to filter level
)
AS
BEGIN
DECLARE @lvl AS INT;
SET @lvl = 0; -- Initialize level counter with 0
-- Insert root node to @Subs
INSERT INTO @Subs(empid, lvl)
SELECT empid, @lvl FROM dbo.Employees WHERE empid = @root;
WHILE @@rowcount > 0 -- while previous level had rows
BEGIN
SET @lvl = @lvl + 1; -- Increment level counter
-- Insert next level of subordinates to @Subs
INSERT INTO @Subs(empid, lvl)
SELECT C.empid, @lvl
FROM @Subs AS P -- P = Parent
JOIN dbo.Employees AS C -- C = Child
ON P.lvl = @lvl - 1 -- Filter parents from previous level
AND C.mgrid = P.empid;
END
RETURN;
END
GO
-- Node ids of descendants of a given node
SELECT empid, lvl FROM dbo.fn_subordinates1(3) AS S;
-- Descendants of a given node
SELECT E.empid, E.empname, S.lvl
FROM dbo.fn_subordinates1(3) AS S
JOIN dbo.Employees AS E
ON E.empid = S.empid;
-- Leaf nodes underneath a given node
SELECT empid
FROM dbo.fn_subordinates1(3) AS P
WHERE NOT EXISTS
(SELECT * FROM dbo.Employees AS C
WHERE C.mgrid = P.empid);
-- Listing 9-5: Subtree of a Given Root, CTE Solution
DECLARE @root AS INT;
SET @root = 3;
WITH SubsCTE
AS
(
-- Anchor member returns root node
SELECT empid, empname, 0 AS lvl
FROM dbo.Employees
WHERE empid = @root
UNION ALL
-- Recursive member returns next level of children
SELECT C.empid, C.empname, P.lvl + 1
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
)
SELECT * FROM SubsCTE;
-- Listing 9-6: Creation Script for Function fn_partsexplosion
---------------------------------------------------------------------
-- Function: fn_partsexplosion, Parts Explosion
--
-- Input : @root INT: Root part id
--
-- Output : @PartsExplosion Table:
-- id and level of contained parts of input part
-- in all levels
--
-- Process : * Insert into @PartsExplosion row of input root part
-- * In a loop, while previous insert loaded more than 0 rows
-- insert into @PartsExplosion next level of parts
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.fn_partsexplosion') IS NOT NULL
DROP FUNCTION dbo.fn_partsexplosion;
GO
CREATE FUNCTION dbo.fn_partsexplosion(@root AS INT)
RETURNS @PartsExplosion Table
(
partid INT NOT NULL,
qty DECIMAL(8, 2) NOT NULL,
unit VARCHAR(3) NOT NULL,
lvl INT NOT NULL,
n INT NOT NULL IDENTITY, -- surrogate key
UNIQUE CLUSTERED(lvl, n) -- Index will be used to filter lvl
)
AS
BEGIN
DECLARE @lvl AS INT;
SET @lvl = 0; -- Initialize level counter with 0
-- Insert root node to @PartsExplosion
INSERT INTO @PartsExplosion(partid, qty, unit, lvl)
SELECT partid, qty, unit, @lvl
FROM dbo.BOM
WHERE partid = @root;
WHILE @@rowcount > 0 -- while previous level had rows
BEGIN
SET @lvl = @lvl + 1; -- Increment level counter
-- Insert next level of subordinates to @PartsExplosion
INSERT INTO @PartsExplosion(partid, qty, unit, lvl)
SELECT C.partid, P.qty * C.qty, C.unit, @lvl
FROM @PartsExplosion AS P -- P = Parent
JOIN dbo.BOM AS C -- C = Child
ON P.lvl = @lvl - 1 -- Filter parents from previous level
AND C.assemblyid = P.partid;
END
RETURN;
END
GO
-- Parts Explosion
SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl
FROM dbo.fn_partsexplosion(2) AS PE
JOIN dbo.Parts AS P
ON P.partid = PE.partid;
-- Listing 9-7: CTE Solution for Parts Explosion
DECLARE @root AS INT;
SET @root = 2;
WITH PartsExplosionCTE
AS
(
-- Anchor member returns root part
SELECT partid, qty, unit, 0 AS lvl
FROM dbo.BOM
WHERE partid = @root
UNION ALL
-- Recursive member returns next level of parts
SELECT C.partid, CAST(P.qty * C.qty AS DECIMAL(8, 2)),
C.unit, P.lvl + 1
FROM PartsExplosionCTE AS P
JOIN dbo.BOM AS C
ON C.assemblyid = P.partid
)
SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl
FROM PartsExplosionCTE AS PE
JOIN dbo.Parts AS P
ON P.partid = PE.partid;
-- Parts Explosion, Aggregating Parts
SELECT P.partid, P.partname, PES.qty, PES.unit
FROM (SELECT partid, unit, SUM(qty) AS qty
FROM dbo.fn_partsexplosion(2) AS PE
GROUP BY partid, unit) AS PES
JOIN dbo.Parts AS P
ON P.partid = PES.partid;
SELECT P.partid, P.partname, PES.qty, PES.unit
FROM (SELECT partid, unit, SUM(qty) AS qty
FROM dbo.fn_partsexplosion(5) AS PE
GROUP BY partid, unit) AS PES
JOIN dbo.Parts AS P
ON P.partid = PES.partid;
-- Listing 9-8: Creation Script for Function fn_subordinates2
---------------------------------------------------------------------
-- Function: fn_subordinates2,
-- Descendants with optional level limit
--
-- Input : @root INT: Manager id
-- @maxlevels INT: Max number of levels to return
--
-- Output : @Subs TABLE: id and level of subordinates of
-- input manager in all levels <= @maxlevels
--
-- Process : * Insert into @Subs row of input manager
-- * In a loop, while previous insert loaded more than 0 rows
-- and previous level is smaller than @maxlevels
-- insert into @Subs next level of subordinates
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.fn_subordinates2') IS NOT NULL
DROP FUNCTION dbo.fn_subordinates2;
GO
CREATE FUNCTION dbo.fn_subordinates2
(@root AS INT, @maxlevels AS INT = NULL) RETURNS @Subs TABLE
(
empid INT NOT NULL PRIMARY KEY NONCLUSTERED,
lvl INT NOT NULL,
UNIQUE CLUSTERED(lvl, empid) -- Index will be used to filter level
)
AS
BEGIN
DECLARE @lvl AS INT;
SET @lvl = 0; -- Initialize level counter with 0
-- If input @maxlevels is NULL, set it to maximum integer
-- to virtually have no limit on levels
SET @maxlevels = COALESCE(@maxlevels, 2147483647);
-- Insert root node to @Subs
INSERT INTO @Subs(empid, lvl)
SELECT empid, @lvl FROM dbo.Employees WHERE empid = @root;
WHILE @@rowcount > 0 -- while previous level had rows
AND @lvl < @maxlevels -- and previous level < @maxlevels
BEGIN
SET @lvl = @lvl + 1; -- Increment level counter
-- Insert next level of subordinates to @Subs
INSERT INTO @Subs(empid, lvl)
SELECT C.empid, @lvl
FROM @Subs AS P -- P = Parent
JOIN dbo.Employees AS C -- C = Child
ON P.lvl = @lvl - 1 -- Filter parents from previous level
AND C.mgrid = P.empid;
END
RETURN;
END
GO
-- Descendants of a given node, no limit on levels
SELECT empid, lvl
FROM dbo.fn_subordinates2(3, NULL) AS S;
-- Descendants of a given node, limit 2 levels
SELECT empid, lvl
FROM dbo.fn_subordinates2(3, 2) AS S;
-- Descendants that are 2 levels underneath a given node
SELECT empid
FROM dbo.fn_subordinates2(3, 2) AS S
WHERE lvl = 2;
GO
-- Listing 9-9: Subtree with level limit, CTE Solution, with MAXRECURSION
DECLARE @root AS INT;
SET @root = 3;
WITH SubsCTE
AS
(
SELECT empid, empname, 0 AS lvl
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, P.lvl + 1
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
)
SELECT * FROM SubsCTE
OPTION (MAXRECURSION 2);
GO
-- Listing 9-10: Subtree with level limit, CTE Solution, with level column
DECLARE @root AS INT, @maxlevels AS INT;
SET @root = 3;
SET @maxlevels = 2;
WITH SubsCTE
AS
(
SELECT empid, empname, 0 AS lvl
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, P.lvl + 1
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
AND P.lvl < @maxlevels -- limit parent's level
)
SELECT * FROM SubsCTE;
---------------------------------------------------------------------
-- Sub-Path
---------------------------------------------------------------------
-- Listing 9-11: Creation Script for Function fn_managers
---------------------------------------------------------------------
-- Function: fn_managers, Ancestors with optional level limit
--
-- Input : @empid INT : Employee id
-- @maxlevels : Max number of levels to return
--
-- Output : @Mgrs Table: id and level of managers of
-- input employee in all levels <= @maxlevels
--
-- Process : * In a loop, while current manager is not null
-- and previous level is smaller than @maxlevels
-- insert into @Mgrs current manager,
-- and get next level manager
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.fn_managers') IS NOT NULL
DROP FUNCTION dbo.fn_managers;
GO
CREATE FUNCTION dbo.fn_managers
(@empid AS INT, @maxlevels AS INT = NULL) RETURNS @Mgrs TABLE
(
empid INT NOT NULL PRIMARY KEY,
lvl INT NOT NULL
)
AS
BEGIN
IF NOT EXISTS(SELECT * FROM dbo.Employees WHERE empid = @empid)
RETURN;
DECLARE @lvl AS INT;
SET @lvl = 0; -- Initialize level counter with 0
-- If input @maxlevels is NULL, set it to maximum integer
-- to virtually have no limit on levels
SET @maxlevels = COALESCE(@maxlevels, 2147483647);
WHILE @empid IS NOT NULL -- while current employee has a manager
AND @lvl <= @maxlevels -- and previous level < @maxlevels
BEGIN
-- Insert current manager to @Mgrs
INSERT INTO @Mgrs(empid, lvl) VALUES(@empid, @lvl);
SET @lvl = @lvl + 1; -- Increment level counter
-- Get next level manager
SET @empid = (SELECT mgrid FROM dbo.Employees WHERE empid = @empid);
END
RETURN;
END
GO
-- Ancestors of a given node, no limit on levels
SELECT empid, lvl
FROM dbo.fn_managers(8, NULL) AS M;
-- Listing 9-12: Ancestors of a Given Node, CTE Solution
-- Ancestors of a given node, CTE Solution
DECLARE @empid AS INT;
SET @empid = 8;
WITH MgrsCTE
AS
(
SELECT empid, mgrid, empname, 0 AS lvl
FROM dbo.Employees
WHERE empid = @empid
UNION ALL
SELECT P.empid, P.mgrid, P.empname, C.lvl + 1
FROM MgrsCTE AS C
JOIN dbo.Employees AS P
ON C.mgrid = P.empid
)
SELECT * FROM MgrsCTE;
-- Ancestors of a given node, limit 2 levels
SELECT empid, lvl
FROM dbo.fn_managers(8, 2) AS M;
GO
-- Listing 9-13: Ancestors with Level Limit, CTE Solution
DECLARE @empid AS INT, @maxlevels AS INT;
SET @empid = 8;
SET @maxlevels = 2;
WITH MgrsCTE
AS
(
SELECT empid, mgrid, empname, 0 AS lvl
FROM dbo.Employees
WHERE empid = @empid
UNION ALL
SELECT P.empid, P.mgrid, P.empname, C.lvl + 1
FROM MgrsCTE AS C
JOIN dbo.Employees AS P
ON C.mgrid = P.empid
AND C.lvl < @maxlevels -- limit child's level
)
SELECT * FROM MgrsCTE;
-- Ancestor that is 2 levels above a given node
SELECT empid
FROM dbo.fn_managers(8, 2) AS M
WHERE lvl = 2;
GO
---------------------------------------------------------------------
-- Subtree/Subgraph with Path Enumeration
---------------------------------------------------------------------
-- Listing 9-14: Creation Script for Function fn_subordinates3
---------------------------------------------------------------------
-- Function: fn_subordinates3,
-- Descendants with optional level limit,
-- and path enumeration
--
-- Input : @root INT: Manager id
-- @maxlevels INT: Max number of levels to return
--
-- Output : @Subs TABLE: id, level and materialized ancestors path
-- of subordinates of input manager
-- in all levels <= @maxlevels
--
-- Process : * Insert into @Subs row of input manager
-- * In a loop, while previous insert loaded more than 0 rows
-- and previous level is smaller than @maxlevels:
-- - insert into @Subs next level of subordinates
-- - calculate a materialized ancestors path for each
-- by concatenating current node id to parent's path
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.fn_subordinates3') IS NOT NULL
DROP FUNCTION dbo.fn_subordinates3;
GO
CREATE FUNCTION dbo.fn_subordinates3
(@root AS INT, @maxlevels AS INT = NULL) RETURNS @Subs TABLE
(
empid INT NOT NULL PRIMARY KEY NONCLUSTERED,
lvl INT NOT NULL,
path VARCHAR(900) NOT NULL
UNIQUE CLUSTERED(lvl, empid) -- Index will be used to filter level
)
AS
BEGIN
DECLARE @lvl AS INT;
SET @lvl = 0; -- Initialize level counter with 0
-- If input @maxlevels is NULL, set it to maximum integer
-- to virtually have no limit on levels
SET @maxlevels = COALESCE(@maxlevels, 2147483647);
-- Insert root node to @Subs
INSERT INTO @Subs(empid, lvl, path)
SELECT empid, @lvl, '.' + CAST(empid AS VARCHAR(10)) + '.'
FROM dbo.Employees WHERE empid = @root;
WHILE @@rowcount > 0 -- while previous level had rows
AND @lvl < @maxlevels -- and previous level < @maxlevels
BEGIN
SET @lvl = @lvl + 1; -- Increment level counter
-- Insert next level of subordinates to @Subs
INSERT INTO @Subs(empid, lvl, path)
SELECT C.empid, @lvl,
P.path + CAST(C.empid AS VARCHAR(10)) + '.'
FROM @Subs AS P -- P = Parent
JOIN dbo.Employees AS C -- C = Child
ON P.lvl = @lvl - 1 -- Filter parents from previous level
AND C.mgrid = P.empid;
END
RETURN;
END
GO
-- Return descendants of a given node, along with a materialized path
SELECT empid, lvl, path
FROM dbo.fn_subordinates3(1, NULL) AS S;
-- Return descendants of a given node, sorted and indented
SELECT E.empid, REPLICATE(' | ', lvl) + empname AS empname
FROM dbo.fn_subordinates3(1, NULL) AS S
JOIN dbo.Employees AS E
ON E.empid = S.empid
ORDER BY path;
-- Listing 9-15: Subtree with Path Enumeration, CTE Solution
-- Descendants of a given node, with Materialized Path, CTE Solution
DECLARE @root AS INT;
SET @root = 1;
WITH SubsCTE
AS
(
SELECT empid, empname, 0 AS lvl,
-- Path of root = '.' + empid + '.'
CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, P.lvl + 1,
-- Path of child = parent's path + child empid + '.'
CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
)
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname
FROM SubsCTE
ORDER BY path;
---------------------------------------------------------------------
-- Sorting
---------------------------------------------------------------------
-- Listing 9-16: Creation Script for Procedure usp_sortsubs
---------------------------------------------------------------------
-- Stored Procedure: usp_sortsubs,
-- Descendants with optional level limit and sort values
--
-- Input : @root INT: Manager id
-- @maxlevels INT: Max number of levels to return
-- @orderby sysname: determines sort order
--
-- Output : Rowset: id, level and sort values
-- of subordinates of input manager
-- in all levels <= @maxlevels
--
-- Process : * Use a loop to load the desired subtree into #SubsPath
-- * For each node, construct a binary sort path
-- * The row number represents the node's position among
-- siblings based on the input ORDER BY list
-- * Load the rows from #SubPath into #SubsSort sorted
-- by the binary sortpath
-- * IDENTITY values representing the global sort value
-- in the subtree will be generated in the target
-- #SubsSort table
-- * Return all rows from #SubsSort sorted by the
-- sort value
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.usp_sortsubs') IS NOT NULL
DROP PROC dbo.usp_sortsubs;
GO
CREATE PROC dbo.usp_sortsubs
@root AS INT = NULL,
@maxlevels AS INT = NULL,
@orderby AS sysname = N'empid'
AS
SET NOCOUNT ON;
-- #SubsPath is a temp table that will hold binary sort paths
CREATE TABLE #SubsPath
(
rownum INT NOT NULL IDENTITY,
nodeid INT NOT NULL,
lvl INT NOT NULL,
sortpath VARBINARY(900) NULL
);
CREATE UNIQUE CLUSTERED INDEX idx_uc_lvl_empid ON #SubsPath(lvl, nodeid);
-- #SubsPath is a temp table that will hold the final
-- integer sort values
CREATE TABLE #SubsSort
(
nodeid INT NOT NULL,
lvl INT NOT NULL,
sortval INT NOT NULL IDENTITY
);
CREATE UNIQUE CLUSTERED INDEX idx_uc_sortval ON #SubsSort(sortval);
-- If @root is not specified, set it to root of the tree
IF @root IS NULL
SET @root = (SELECT empid FROM dbo.Employees WHERE mgrid IS NULL);
-- If @maxlevels is not specified, set it maximum integer
IF @maxlevels IS NULL
SET @maxlevels = 2147483647;
DECLARE @lvl AS INT, @sql AS NVARCHAR(4000);
SET @lvl = 0;
-- Load row for input root to #SubsPath
-- The root's sort path is simply 1 converted to binary
INSERT INTO #SubsPath(nodeid, lvl, sortpath)
SELECT empid, @lvl, CAST(1 AS BINARY(4))
FROM dbo.Employees
WHERE empid = @root;
-- Form a loop to load the next level of suboridnates
-- to #SubsPath in each iteration
WHILE @@rowcount > 0 AND @lvl < @maxlevels
BEGIN
SET @lvl = @lvl + 1;
-- Insert next level of subordinates
-- Initially, just copy parent's path to child
-- Note that IDENTITY values will be generated in #SubsPath
-- based on input order by list
--
-- Then update the path of the employees in the current level
-- to their parent's path + their rownum converted to binary
INSERT INTO #SubsPath(nodeid, lvl, sortpath)
SELECT C.empid, @lvl, P.sortpath
FROM #SubsPath AS P
JOIN dbo.Employees AS C
ON P.lvl = @lvl - 1
AND C.mgrid = P.nodeid
ORDER BY -- determines order of siblings
CASE WHEN @orderby = N'empid' THEN empid END,
CASE WHEN @orderby = N'empname' THEN empname END,
CASE WHEN @orderby = N'salary' THEN salary END;
UPDATE #SubsPath
SET sortpath = sortpath + CAST(rownum AS BINARY(4))
WHERE lvl = @lvl;
END
-- Load the rows from #SubsPath to @SubsSort sorted by the binary
-- sort path
-- The target identity values in the sortval column will represent
-- the global sort value of the nodes within the result subtree
INSERT INTO #SubsSort(nodeid, lvl)
SELECT nodeid, lvl FROM #SubsPath ORDER BY sortpath;
-- Return for each node the id, level and sort value
SELECT nodeid AS empid, lvl, sortval FROM #SubsSort
ORDER BY sortval;
GO
-- Get all employees with sort values by empname
-- (relying on proc's defaults)
EXEC dbo.usp_sortsubs @orderby = N'empname';
-- Get 3 levels of subordinates underneath employee 1
-- with sort values by empname
EXEC dbo.usp_sortsubs
@root = 1,
@maxlevels = 3,
@orderby = N'empname';
GO
-- Listing 9-17: Script Returning All Employees, Sorted by empname
CREATE TABLE #Subs
(
empid INT NULL,
lvl INT NULL,
sortval INT NULL
);
CREATE UNIQUE CLUSTERED INDEX idx_uc_sortval ON #Subs(sortval);
-- By empname
INSERT INTO #Subs(empid, lvl, sortval)
EXEC dbo.usp_sortsubs
@orderby = N'empname';
SELECT E.empid, REPLICATE(' | ', lvl) + E.empname AS empname
FROM #Subs AS S
JOIN dbo.Employees AS E
ON S.empid = E.empid
ORDER BY sortval;
-- Listing 9-18: Script Returning All Employees, Sorted by salary
TRUNCATE TABLE #Subs;
INSERT INTO #Subs(empid, lvl, sortval)
EXEC dbo.usp_sortsubs
@orderby = N'salary';
SELECT E.empid, salary, REPLICATE(' | ', lvl) + E.empname AS empname
FROM #Subs AS S
JOIN dbo.Employees AS E
ON S.empid = E.empid
ORDER BY sortval;
-- Cleanup
DROP TABLE #Subs
GO
-- Listing 9-19: Sorting Hierarchy by empname, CTE Solution
DECLARE @root AS INT;
SET @root = 1;
WITH SubsCTE
AS
(
SELECT empid, empname, 0 AS lvl,
-- Path of root is 1 (binary)
CAST(1 AS VARBINARY(MAX)) AS sortpath
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, P.lvl + 1,
-- Path of child = parent's path + child row number (binary)
P.sortpath + CAST(
ROW_NUMBER() OVER(PARTITION BY C.mgrid
ORDER BY C.empname) -- sort col(s)
AS BINARY(4))
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
)
SELECT empid, ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval,
REPLICATE(' | ', lvl) + empname AS empname
FROM SubsCTE
ORDER BY sortval;
GO
-- Listing 9-20: Sorting Hierarchy by salary, CTE Solution
DECLARE @root AS INT;
SET @root = 1;
WITH SubsCTE
AS
(
SELECT empid, empname, salary, 0 AS lvl,
-- Path of root = 1 (binary)
CAST(1 AS VARBINARY(MAX)) AS sortpath
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, C.salary, P.lvl + 1,
-- Path of child = parent's path + child row number (binary)
P.sortpath + CAST(
ROW_NUMBER() OVER(PARTITION BY C.mgrid
ORDER BY C.salary) -- sort col(s)
AS BINARY(4))
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
)
SELECT empid, salary, ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval,
REPLICATE(' | ', lvl) + empname AS empname
FROM SubsCTE
ORDER BY sortval;
---------------------------------------------------------------------
-- Cycles
---------------------------------------------------------------------
-- Create a cyclic path
UPDATE dbo.Employees SET mgrid = 14 WHERE empid = 1;
GO
-- Listing 9-21: Detecting Cycles, CTE Solution
DECLARE @root AS INT;
SET @root = 1;
WITH SubsCTE
AS
(
SELECT empid, empname, 0 AS lvl,
CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path,
-- Obviously root has no cycle
0 AS cycle
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, P.lvl + 1,
CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path,
-- Cycle detected if parent's path contains child's id
CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'
THEN 1 ELSE 0 END
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
)
SELECT empid, empname, cycle, path
FROM SubsCTE;
GO
-- Listing 9-22: Not Pursuing Cycles, CTE Solution
DECLARE @root AS INT;
SET @root = 1;
WITH SubsCTE
AS
(
SELECT empid, empname, 0 AS lvl,
CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path,
-- Obviously root has no cycle
0 AS cycle
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, P.lvl + 1,
CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path,
-- Cycle detected if parent's path contains child's id
CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'
THEN 1 ELSE 0 END
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
AND P.cycle = 0 -- do not pursue branch for parent with cycle
)
SELECT empid, empname, cycle, path
FROM SubsCTE;
GO
-- Listing 9-23: Isolating Cyclic Paths, CTE Solution
DECLARE @root AS INT;
SET @root = 1;
WITH SubsCTE
AS
(
SELECT empid, empname, 0 AS lvl,
CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path,
-- Obviously root has no cycle
0 AS cycle
FROM dbo.Employees
WHERE empid = @root
UNION ALL
SELECT C.empid, C.empname, P.lvl + 1,
CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
AS VARCHAR(MAX)) AS path,
-- Cycle detected if parent's path contains child's id
CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'
THEN 1 ELSE 0 END
FROM SubsCTE AS P
JOIN dbo.Employees AS C
ON C.mgrid = P.empid
AND P.cycle = 0
)
SELECT path FROM SubsCTE WHERE cycle = 1;
-- Fix cyclic path
UPDATE dbo.Employees SET mgrid = NULL WHERE empid = 1;
---------------------------------------------------------------------
-- Materialized Path
---------------------------------------------------------------------
---------------------------------------------------------------------
-- Maintaining Data
---------------------------------------------------------------------
-- Listing 9-24: DDL for Employees with Path
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Employees') IS NOT NULL
DROP TABLE dbo.Employees;
GO
CREATE TABLE dbo.Employees
(
empid INT NOT NULL PRIMARY KEY NONCLUSTERED,
mgrid INT NULL REFERENCES dbo.Employees,
empname VARCHAR(25) NOT NULL,
salary MONEY NOT NULL,
lvl INT NOT NULL,
path VARCHAR(900) NOT NULL UNIQUE CLUSTERED
);
CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid);
GO
---------------------------------------------------------------------
-- Adding Employees who Manage No One (Leaves)
---------------------------------------------------------------------
-- Listing 9-25: Creation Script for Procedure usp_insertemp
---------------------------------------------------------------------
-- Stored Procedure: usp_insertemp,
-- Inserts new employee who manages no one into the table
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.usp_insertemp') IS NOT NULL
DROP PROC dbo.usp_insertemp;
GO
CREATE PROC dbo.usp_insertemp
@empid INT,
@mgrid INT,
@empname VARCHAR(25),
@salary MONEY
AS
SET NOCOUNT ON;
-- Handle case where the new employee has no manager (root)
IF @mgrid IS NULL
INSERT INTO dbo.Employees(empid, mgrid, empname, salary, lvl, path)
VALUES(@empid, @mgrid, @empname, @salary,
0, '.' + CAST(@empid AS VARCHAR(10)) + '.');
-- Handle subordinate case (non-root)
ELSE
INSERT INTO dbo.Employees(empid, mgrid, empname, salary, lvl, path)
SELECT @empid, @mgrid, @empname, @salary,
lvl + 1, path + CAST(@empid AS VARCHAR(10)) + '.'
FROM dbo.Employees
WHERE empid = @mgrid;
GO
-- Listing 9-26: Sample Data for Employees with Path
EXEC dbo.usp_insertemp
@empid = 1, @mgrid = NULL, @empname = 'David', @salary = $10000.00;
EXEC dbo.usp_insertemp
@empid = 2, @mgrid = 1, @empname = 'Eitan', @salary = $7000.00;
EXEC dbo.usp_insertemp
@empid = 3, @mgrid = 1, @empname = 'Ina', @salary = $7500.00;
EXEC dbo.usp_insertemp
@empid = 4, @mgrid = 2, @empname = 'Seraph', @salary = $5000.00;
EXEC dbo.usp_insertemp
@empid = 5, @mgrid = 2, @empname = 'Jiru', @salary = $5500.00;
EXEC dbo.usp_insertemp
@empid = 6, @mgrid = 2, @empname = 'Steve', @salary = $4500.00;
EXEC dbo.usp_insertemp
@empid = 7, @mgrid = 3, @empname = 'Aaron', @salary = $5000.00;
EXEC dbo.usp_insertemp
@empid = 8, @mgrid = 5, @empname = 'Lilach', @salary = $3500.00;
EXEC dbo.usp_insertemp
@empid = 9, @mgrid = 7, @empname = 'Rita', @salary = $3000.00;
EXEC dbo.usp_insertemp
@empid = 10, @mgrid = 5, @empname = 'Sean', @salary = $3000.00;
EXEC dbo.usp_insertemp
@empid = 11, @mgrid = 7, @empname = 'Gabriel', @salary = $3000.00;
EXEC dbo.usp_insertemp
@empid = 12, @mgrid = 9, @empname = 'Emilia', @salary = $2000.00;
EXEC dbo.usp_insertemp
@empid = 13, @mgrid = 9, @empname = 'Michael', @salary = $2000.00;
EXEC dbo.usp_insertemp
@empid = 14, @mgrid = 9, @empname = 'Didi', @salary = $1500.00;
GO
-- Examine data after load
SELECT empid, mgrid, empname, salary, lvl, path
FROM dbo.Employees
ORDER BY path;
---------------------------------------------------------------------
-- Moving a Subtree
---------------------------------------------------------------------
-- Listing 9-27: Creation Script for Procedure usp_movesubtree
---------------------------------------------------------------------
-- Stored Procedure: usp_movesubtree,
-- Moves a whole subtree of a given root to a new location
-- under a given manager
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.usp_movesubtree') IS NOT NULL
DROP PROC dbo.usp_movesubtree;
GO
CREATE PROC dbo.usp_movesubtree
@root INT,
@mgrid INT
AS
SET NOCOUNT ON;
BEGIN TRAN;
-- Update level and path of all employees in the subtree (E)
-- Set level =
-- current level + new manager's level - old manager's level
-- Set path =
-- in current path remove old manager's path
-- and substitute with new manager's path
UPDATE E
SET lvl = E.lvl + NM.lvl - OM.lvl,
path = STUFF(E.path, 1, LEN(OM.path), NM.path)
FROM dbo.Employees AS E -- E = Employees (subtree)
JOIN dbo.Employees AS R -- R = Root (one row)
ON R.empid = @root
AND E.path LIKE R.path + '%'
JOIN dbo.Employees AS OM -- OM = Old Manager (one row)
ON OM.empid = R.mgrid
JOIN dbo.Employees AS NM -- NM = New Manager (one row)
ON NM.empid = @mgrid;
-- Update root's new manager
UPDATE dbo.Employees SET mgrid = @mgrid WHERE empid = @root;
COMMIT TRAN;
GO
-- Before moving subtree
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
FROM dbo.Employees
ORDER BY path;
-- Move Subtree
BEGIN TRAN;
EXEC dbo.usp_movesubtree
@root = 7,
@mgrid = 10;
-- After moving subtree
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
FROM dbo.Employees
ORDER BY path;
ROLLBACK TRAN; -- rollback used in order not to apply the change
---------------------------------------------------------------------
-- Removing a Subtree
---------------------------------------------------------------------
-- Before deleteting subtree
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
FROM dbo.Employees
ORDER BY path;
-- Delete Subtree
BEGIN TRAN;
DELETE FROM dbo.Employees
WHERE path LIKE
(SELECT M.path + '%'
FROM dbo.Employees as M
WHERE M.empid = 7);
-- After deleting subtree
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
FROM dbo.Employees
ORDER BY path;
ROLLBACK TRAN; -- rollback used in order not to apply the change
---------------------------------------------------------------------
-- Querying Materialized Path
---------------------------------------------------------------------
-- Subtree of a given root
SELECT REPLICATE(' | ', E.lvl - M.lvl) + E.empname
FROM dbo.Employees AS E
JOIN dbo.Employees AS M
ON M.empid = 3 -- root
AND E.path LIKE M.path + '%'
ORDER BY E.path;
-- Subtree of a given root, excluding root
SELECT REPLICATE(' | ', E.lvl - M.lvl - 1) + E.empname
FROM dbo.Employees AS E
JOIN dbo.Employees AS M
ON M.empid = 3
AND E.path LIKE M.path + '_%'
ORDER BY E.path;
-- Leaf nodes under a given root
SELECT E.empid, E.empname
FROM dbo.Employees AS E
JOIN dbo.Employees AS M
ON M.empid = 3
AND E.path LIKE M.path + '%'
WHERE NOT EXISTS
(SELECT *
FROM dbo.Employees AS E2
WHERE E2.mgrid = E.empid);
-- Subtree of a given root, limit number of levels
SELECT REPLICATE(' | ', E.lvl - M.lvl) + E.empname
FROM dbo.Employees AS E
JOIN dbo.Employees AS M
ON M.empid = 3
AND E.path LIKE M.path + '%'
AND E.lvl - M.lvl <= 2
ORDER BY E.path;
-- Nodes that are n levels under a given root
SELECT E.empid, E.empname
FROM dbo.Employees AS E
JOIN dbo.Employees AS M
ON M.empid = 3
AND E.path LIKE M.path + '%'
AND E.lvl - M.lvl = 2;
-- Ancestors of a given node (requires a table scan)
SELECT REPLICATE(' | ', M.lvl) + M.empname
FROM dbo.Employees AS E
JOIN dbo.Employees AS M
ON E.empid = 14
AND E.path LIKE M.path + '%'
ORDER BY E.path;
-- Listing 9-28: Creating and Populating Auxiliary Table of Numbers
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Nums') IS NOT NULL
DROP TABLE dbo.Nums;
GO
CREATE TABLE dbo.Nums(n INT NOT NULL PRIMARY KEY);
DECLARE @max AS INT, @rc AS INT;
SET @max = 8000;
SET @rc = 1;
INSERT INTO Nums VALUES(1);
WHILE @rc * 2 <= @max
BEGIN
INSERT INTO dbo.Nums SELECT n + @rc FROM dbo.Nums;
SET @rc = @rc * 2;
END
INSERT INTO dbo.Nums
SELECT n + @rc FROM dbo.Nums WHERE n + @rc <= @max;
GO
-- Listing 9-29: Creation Script for Function fn_splitpath
USE tempdb;
GO
IF OBJECT_ID('dbo.fn_splitpath') IS NOT NULL
DROP FUNCTION dbo.fn_splitpath;
GO
CREATE FUNCTION dbo.fn_splitpath(@empid AS INT) RETURNS TABLE
AS
RETURN
SELECT
n - LEN(REPLACE(LEFT(path, n), '.', '')) AS pos,
CAST(SUBSTRING(path, n + 1,
CHARINDEX('.', path, n+1) - n - 1) AS INT) AS empid
FROM dbo.Employees
JOIN dbo.Nums
ON empid = @empid
AND n < LEN(path)
AND SUBSTRING(path, n, 1) = '.'
GO
-- Test fn_splitpath function
SELECT pos, empid FROM dbo.fn_splitpath(14);
-- Getting ancestors using fn_splitpath function
SELECT REPLICATE(' | ', lvl) + empname
FROM dbo.fn_splitpath(14) AS SP
JOIN dbo.Employees AS E
ON E.empid = SP.empid
ORDER BY path;
---------------------------------------------------------------------
-- Nested Sets
---------------------------------------------------------------------
---------------------------------------------------------------------
-- Assigning Left and Right Values
---------------------------------------------------------------------
-- Listing 9-30: Producing Binary Sort Paths Representing Nested Sets Relationships
USE tempdb;
GO
-- Create index to speed sorting siblings by empname, empid
CREATE UNIQUE INDEX idx_unc_mgrid_empname_empid
ON dbo.Employees(mgrid, empname, empid);
GO
DECLARE @root AS INT;
SET @root = 1;
-- CTE with two numbers: 1 and 2
WITH TwoNumsCTE
AS
(
SELECT 1 AS n UNION ALL SELECT 2
),
-- CTE with two binary sort paths for each node:
-- One smaller than descendants sort paths
-- One greater than descendants sort paths
SortPathCTE
AS
(
SELECT empid, 0 AS lvl, n,
CAST(n AS VARBINARY(MAX)) AS sortpath
FROM dbo.Employees CROSS JOIN TwoNumsCTE
WHERE empid = @root
UNION ALL
SELECT C.empid, P.lvl + 1, TN.n,
P.sortpath + CAST(
(-1+ROW_NUMBER() OVER(PARTITION BY C.mgrid
-- *** determines order of siblings ***
ORDER BY C.empname, C.empid))/2*2+TN.n
AS BINARY(4))
FROM SortPathCTE AS P
JOIN dbo.Employees AS C
ON P.n = 1
AND C.mgrid = P.empid
CROSS JOIN TwoNumsCTE AS TN
)
SELECT * FROM SortPathCTE
ORDER BY sortpath;
GO
-- Listing 9-31: CTE Code That Creates Nested Sets Relationships
DECLARE @root AS INT;
SET @root = 1;
-- CTE with two numbers: 1 and 2
WITH TwoNumsCTE
AS
(
SELECT 1 AS n UNION ALL SELECT 2
),
-- CTE with two binary sort paths for each node:
-- One smaller than descendants sort paths
-- One greater than descendants sort paths
SortPathCTE
AS
(
SELECT empid, 0 AS lvl, n,
CAST(n AS VARBINARY(MAX)) AS sortpath
FROM dbo.Employees CROSS JOIN TwoNumsCTE
WHERE empid = @root
UNION ALL
SELECT C.empid, P.lvl + 1, TN.n,
P.sortpath + CAST(
ROW_NUMBER() OVER(PARTITION BY C.mgrid
-- *** determines order of siblings ***
ORDER BY C.empname, C.empid, TN.n)
AS BINARY(4))
FROM SortPathCTE AS P
JOIN dbo.Employees AS C
ON P.n = 1
AND C.mgrid = P.empid
CROSS JOIN TwoNumsCTE AS TN
),
-- CTE with Row Numbers Representing sortpath Order
SortCTE
AS
(
SELECT empid, lvl,
ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval
FROM SortPathCTE
),
-- CTE with Left and Right Values Representing
-- Nested Sets Relationships
NestedSetsCTE
AS
(
SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt
FROM SortCTE
GROUP BY empid, lvl
)
SELECT * FROM NestedSetsCTE
ORDER BY lft;
GO
-- Listing 9-32: Creation Script for the Function fn_empsnestedsets
---------------------------------------------------------------------
-- Function: fn_empsnestedsets, Nested Sets Relationships
--
-- Input : @root INT: Root of subtree
--
-- Output : @NestedSets Table: employee id, level in the subtree,
-- left and right values representing
-- nested sets relationships
--
-- Process : * Loads subtree into @SortPath,
-- first root, then a level at a time.
-- Note: two instances of each employee are loaded;
-- one representing left arm (n = 1),
-- and one representing right (n = 2).
-- For each employee and arm, a binary path is constructed,
-- representing the nested sets poition.
-- The binary path has 4 bytes for each of the employee's
-- ancestors. For each ancestor, the 4 bytes represent
-- its position in the level (calculated with identity).
-- Finally @SortPath will contain a pair of rows for each
-- employee along with a sort path represeting the arm's
-- nested sets position.
-- * Next, the rows from @SortPath are loaded
-- into @SortVals, sorted by sortpath. After the load,
-- an integer identity column sortval holds sort values
-- representing the nested sets position of each arm.
-- * The data from @SortVals is grouped by employee
-- generating the left and right values for each employee
-- in one row. The resultset is loaded into the
-- @NestedSets table, which is the function's output.
--
---------------------------------------------------------------------
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.fn_empsnestedsets') IS NOT NULL
DROP FUNCTION dbo.fn_empsnestedsets;
GO
CREATE FUNCTION dbo.fn_empsnestedsets(@root AS INT)
RETURNS @NestedSets TABLE
(
empid INT NOT NULL PRIMARY KEY,
lvl INT NOT NULL,
lft INT NOT NULL,
rgt INT NOT NULL
)
AS
BEGIN
DECLARE @lvl AS INT;
SET @lvl = 0;
-- @TwoNums: Table Variable with two numbers: 1 and 2
DECLARE @TwoNums TABLE(n INT NOT NULL PRIMARY KEY);
INSERT INTO @TwoNums(n) SELECT 1 AS n UNION ALL SELECT 2;
-- @SortPath: Table Variable with two binary sort paths
-- for each node:
-- One smaller than descendants sort paths
-- One greater than descendants sort paths
DECLARE @SortPath TABLE
(
empid INT NOT NULL,
lvl INT NOT NULL,
n INT NOT NULL,
sortpath VARBINARY(900) NOT NULL,
rownum INT NOT NULL IDENTITY,
UNIQUE(lvl, n, empid)
);
-- Load root into @SortPath
INSERT INTO @SortPath(empid, lvl, n, sortpath)
SELECT empid, @lvl, n,
CAST(n AS BINARY(4)) AS sortpath
FROM dbo.Employees CROSS JOIN @TwoNums
WHERE empid = @root
WHILE @@rowcount > 0
BEGIN
SET @lvl = @lvl + 1;
-- Load next level into @SortPath
INSERT INTO @SortPath(empid, lvl, n, sortpath)
SELECT C.empid, @lvl, TN.n, P.sortpath
FROM @SortPath AS P
JOIN dbo.Employees AS C
ON P.lvl = @lvl - 1
AND P.n = 1
AND C.mgrid = P.empid
CROSS JOIN @TwoNums AS TN
-- *** Determines order of siblings ***
ORDER BY C.empname, C.empid, TN.n;
-- Update sort path to include child's position
UPDATE @SortPath
SET sortpath = sortpath + CAST(rownum AS BINARY(4))
WHERE lvl = @lvl;
END
-- @SortVals: Table Variable with row numbers
-- representing sortpath order
DECLARE @SortVals TABLE
(
empid INT NOT NULL,
lvl INT NOT NULL,
sortval INT NOT NULL IDENTITY
)
-- Load data from @SortPath sorted by sortpath
-- to generate sort values
INSERT INTO @SortVals(empid, lvl)
SELECT empid, lvl FROM @SortPath ORDER BY sortpath;
-- Load data into @NestedStes generating left and right
-- values representing nested sets relationships
INSERT INTO @NestedSets(empid, lvl, lft, rgt)
SELECT empid, lvl, MIN(sortval), MAX(sortval)
FROM @SortVals
GROUP BY empid, lvl
RETURN;
END
GO
-- Test the fn_empsnestedsets function
SELECT * FROM dbo.fn_empsnestedsets(1)
ORDER BY lft;
GO
-- Listing 9-33: Materializing Nested Sets Relationships in a Table
SET NOCOUNT ON;
USE tempdb;
GO
DECLARE @root AS INT;
SET @root = 1;
WITH TwoNumsCTE
AS
(
SELECT 1 AS n UNION ALL SELECT 2
),
SortPathCTE
AS
(
SELECT empid, 0 AS lvl, n,
CAST(n AS VARBINARY(MAX)) AS sortpath
FROM dbo.Employees CROSS JOIN TwoNumsCTE
WHERE empid = @root
UNION ALL
SELECT C.empid, P.lvl + 1, TN.n,
P.sortpath + CAST(
ROW_NUMBER() OVER(PARTITION BY C.mgrid
-- *** determines order of siblings ***
ORDER BY C.empname, C.empid, TN.n)
AS BINARY(4))
FROM SortPathCTE AS P
JOIN dbo.Employees AS C
ON P.n = 1
AND C.mgrid = P.empid
CROSS JOIN TwoNumsCTE AS TN
),
SortCTE
AS
(
SELECT empid, lvl,
ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval
FROM SortPathCTE
),
NestedSetsCTE
AS
(
SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt
FROM SortCTE
GROUP BY empid, lvl
)
SELECT E.empid, E.empname, E.salary, NS.lvl, NS.lft, NS.rgt
INTO dbo.EmployeesNS
FROM NestedSetsCTE AS NS
JOIN dbo.Employees AS E
ON E.empid = NS.empid;
ALTER TABLE dbo.EmployeesNS ADD PRIMARY KEY NONCLUSTERED(empid);
CREATE UNIQUE CLUSTERED INDEX idx_unc_lft_rgt ON dbo.EmployeesNS(lft, rgt);
GO
---------------------------------------------------------------------
-- Querying
---------------------------------------------------------------------
-- Descendants of a given root
SELECT C.empid, REPLICATE(' | ', C.lvl - P.lvl) + C.empname AS empname
FROM dbo.EmployeesNS AS P
JOIN dbo.EmployeesNS AS C
ON P.empid = 3
AND C.lft >= P.lft AND C.rgt <= P.rgt
ORDER BY C.lft;
-- Descendants of a given root, limiting 2 levels
SELECT C.empid, REPLICATE(' | ', C.lvl - P.lvl) + C.empname AS empname
FROM dbo.EmployeesNS AS P
JOIN dbo.EmployeesNS AS C
ON P.empid = 3
AND C.lft >= P.lft AND C.rgt <= P.rgt
AND C.lvl - P.lvl <= 2
ORDER BY C.lft;
-- Leaf nodes under a given root
SELECT C.empid, C.empname
FROM dbo.EmployeesNS AS P
JOIN dbo.EmployeesNS AS C
ON P.empid = 3
AND C.lft >= P.lft AND C.rgt <= P.rgt
AND C.rgt - C.lft = 1;
-- Count of subordinates of each node
SELECT empid, (rgt - lft - 1) / 2 AS cnt,
REPLICATE(' | ', lvl) + empname AS empname
FROM dbo.EmployeesNS
ORDER BY lft;
-- Ancestors of a given node
SELECT P.empid, P.empname, P.lvl
FROM dbo.EmployeesNS AS P
JOIN dbo.EmployeesNS AS C
ON C.empid = 14
AND C.lft >= P.lft AND C.rgt <= P.rgt;
GO
-- Cleanup
DROP TABLE dbo.EmployeesNS;
GO
---------------------------------------------------------------------
-- Transitive Closure
---------------------------------------------------------------------
---------------------------------------------------------------------
-- Directed Acyclic Graph (DAG)
---------------------------------------------------------------------
-- Listing 9-34: Transitive Closure of BOM (DAG)
WITH BOMTC
AS
(
-- Return all first-level containment relationships
SELECT assemblyid, partid
FROM dbo.BOM
WHERE assemblyid IS NOT NULL
UNION ALL
-- Return next-level containment relationships
SELECT P.assemblyid, C.partid
FROM BOMTC AS P
JOIN dbo.BOM AS C
ON C.assemblyid = P.partid
)
-- Return distinct pairs that have
-- transitive containment relationships
SELECT DISTINCT assemblyid, partid
FROM BOMTC;
GO
-- Listing 9-35: Creation Script for the fn_BOMTC UDF
IF OBJECT_ID('dbo.fn_BOMTC') IS NOT NULL
DROP FUNCTION dbo.fn_BOMTC;
GO
CREATE FUNCTION fn_BOMTC() RETURNS @BOMTC TABLE
(
assemblyid INT NOT NULL,
partid INT NOT NULL,
PRIMARY KEY (assemblyid, partid)
)
AS
BEGIN
INSERT INTO @BOMTC(assemblyid, partid)
SELECT assemblyid, partid
FROM dbo.BOM
WHERE assemblyid IS NOT NULL
WHILE @@rowcount > 0
INSERT INTO @BOMTC
SELECT P.assemblyid, C.partid
FROM @BOMTC AS P
JOIN dbo.BOM AS C
ON C.assemblyid = P.partid
WHERE NOT EXISTS
(SELECT * FROM @BOMTC AS P2
WHERE P2.assemblyid = P.assemblyid
AND P2.partid = C.partid);
RETURN;
END
GO
-- Use the fn_BOMTC UDF
SELECT assemblyid, partid FROM fn_BOMTC();
GO
-- Listing 9-36: All Paths in BOM
WITH BOMPaths
AS
(
SELECT assemblyid, partid,
1 AS distance, -- distance in first level is 1
-- path in first level is .assemblyid.partid.
'.' + CAST(assemblyid AS VARCHAR(MAX)) +
'.' + CAST(partid AS VARCHAR(MAX)) + '.' AS path
FROM dbo.BOM
WHERE assemblyid IS NOT NULL
UNION ALL
SELECT P.assemblyid, C.partid,
-- distance in next level is parent's distance + 1
P.distance + 1,
-- path in next level is parent_path.child_partid.
P.path + CAST(C.partid AS VARCHAR(MAX)) + '.'
FROM BOMPaths AS P
JOIN dbo.BOM AS C
ON C.assemblyid = P.partid
)
-- Return all paths
SELECT * FROM BOMPaths;
-- Listing 9-37: Shortest Paths in BOM
WITH BOMPaths -- All paths
AS
(
SELECT assemblyid, partid,
1 AS distance,
'.' + CAST(assemblyid AS VARCHAR(MAX)) +
'.' + CAST(partid AS VARCHAR(MAX)) + '.' AS path
FROM dbo.BOM
WHERE assemblyid IS NOT NULL
UNION ALL
SELECT P.assemblyid, C.partid,
P.distance + 1,
P.path + CAST(C.partid AS VARCHAR(MAX)) + '.'
FROM BOMPaths AS P
JOIN dbo.BOM AS C
ON C.assemblyid = P.partid
),
BOMMinDist AS -- Minimum distance for each pair
(
SELECT assemblyid, partid, MIN(distance) AS mindist
FROM BOMPaths
GROUP BY assemblyid, partid
)
-- Shortest path for each pair
SELECT BP.*
FROM BOMMinDist AS BMD
JOIN BOMPaths AS BP
ON BMD.assemblyid = BP.assemblyid
AND BMD.partid = BP.partid
AND BMD.mindist = BP.distance;
GO
---------------------------------------------------------------------
-- Undirected Cyclic Graph
---------------------------------------------------------------------
-- Listing 9-38: Transitive Closure of Roads (Undirected Cyclic Graph)
WITH Roads2 -- Two rows for each pair (f-->t, t-->f)
AS
(
SELECT city1 AS from_city, city2 AS to_city FROM dbo.Roads
UNION ALL
SELECT city2, city1 FROM dbo.Roads
),
RoadPaths AS
(
-- Return all first-level reachability pairs
SELECT from_city, to_city,
-- path is needed to identify cycles
CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
FROM Roads2
UNION ALL
-- Return next-level reachability pairs
SELECT F.from_city, T.to_city,
CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
FROM RoadPaths AS F
JOIN Roads2 AS T
-- if to_city appears in from_city's path, cycle detected
ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
THEN 1 ELSE 0 END = 0
AND F.to_city = T.from_city
)
-- Return Transitive Closure of Roads
SELECT DISTINCT from_city, to_city
FROM RoadPaths;
GO
-- Listing 9-39: Creation Script for the fn_RoadsTC UDF
IF OBJECT_ID('dbo.fn_RoadsTC') IS NOT NULL
DROP FUNCTION dbo.fn_RoadsTC;
GO
CREATE FUNCTION dbo.fn_RoadsTC() RETURNS @RoadsTC TABLE (
from_city VARCHAR(3) NOT NULL,
to_city VARCHAR(3) NOT NULL,
PRIMARY KEY (from_city, to_city)
)
AS
BEGIN
DECLARE @added as INT;
INSERT INTO @RoadsTC(from_city, to_city)
SELECT city1, city2 FROM dbo.Roads;
SET @added = @@rowcount;
INSERT INTO @RoadsTC
SELECT city2, city1 FROM dbo.Roads
SET @added = @added + @@rowcount;
WHILE @added > 0 BEGIN
INSERT INTO @RoadsTC
SELECT DISTINCT TC.from_city, R.city2
FROM @RoadsTC AS TC
JOIN dbo.Roads AS R
ON R.city1 = TC.to_city
WHERE NOT EXISTS
(SELECT * FROM @RoadsTC AS TC2
WHERE TC2.from_city = TC.from_city
AND TC2.to_city = R.city2)
AND TC.from_city <> R.city2;
SET @added = @@rowcount;
INSERT INTO @RoadsTC
SELECT DISTINCT TC.from_city, R.city1
FROM @RoadsTC AS TC
JOIN dbo.Roads AS R
ON R.city2 = TC.to_city
WHERE NOT EXISTS
(SELECT * FROM @RoadsTC AS TC2
WHERE TC2.from_city = TC.from_city
AND TC2.to_city = R.city1)
AND TC.from_city <> R.city1;
SET @added = @added + @@rowcount;
END
RETURN;
END
GO
-- Use the fn_RoadsTC UDF
SELECT * FROM dbo.fn_RoadsTC();
GO
-- Listing 9-40: All paths and distances in Roads (15262 rows)
WITH Roads2
AS
(
SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads
UNION ALL
SELECT city2, city1, distance FROM dbo.Roads
),
RoadPaths AS
(
SELECT from_city, to_city, distance,
CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
FROM Roads2
UNION ALL
SELECT F.from_city, T.to_city, F.distance + T.distance,
CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
FROM RoadPaths AS F
JOIN Roads2 AS T
ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
THEN 1 ELSE 0 END = 0
AND F.to_city = T.from_city
)
-- Return all paths and distances
SELECT * FROM RoadPaths;
-- Listing 9-41: Shortest paths in Roads
WITH Roads2
AS
(
SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads
UNION ALL
SELECT city2, city1, distance FROM dbo.Roads
),
RoadPaths AS
(
SELECT from_city, to_city, distance,
CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
FROM Roads2
UNION ALL
SELECT F.from_city, T.to_city, F.distance + T.distance,
CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
FROM RoadPaths AS F
JOIN Roads2 AS T
ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
THEN 1 ELSE 0 END = 0
AND F.to_city = T.from_city
),
RoadsMinDist -- Min distance for each pair in TC
AS
(
SELECT from_city, to_city, MIN(distance) AS mindist
FROM RoadPaths
GROUP BY from_city, to_city
)
-- Return shortest paths and distances
SELECT RP.*
FROM RoadsMinDist AS RMD
JOIN RoadPaths AS RP
ON RMD.from_city = RP.from_city
AND RMD.to_city = RP.to_city
AND RMD.mindist = RP.distance;
GO
-- Listing 9-42: Load Shortest Road Paths Into a Table
WITH Roads2
AS
(
SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads
UNION ALL
SELECT city2, city1, distance FROM dbo.Roads
),
RoadPaths AS
(
SELECT from_city, to_city, distance,
CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
FROM Roads2
UNION ALL
SELECT F.from_city, T.to_city, F.distance + T.distance,
CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
FROM RoadPaths AS F
JOIN Roads2 AS T
ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
THEN 1 ELSE 0 END = 0
AND F.to_city = T.from_city
),
RoadsMinDist
AS
(
SELECT from_city, to_city, MIN(distance) AS mindist
FROM RoadPaths
GROUP BY from_city, to_city
)
SELECT RP.*
INTO dbo.RoadPaths
FROM RoadsMinDist AS RMD
JOIN RoadPaths AS RP
ON RMD.from_city = RP.from_city
AND RMD.to_city = RP.to_city
AND RMD.mindist = RP.distance;
CREATE UNIQUE CLUSTERED INDEX idx_uc_from_city_to_city
ON dbo.RoadPaths(from_city, to_city);
GO
-- Return shortest path between Los Angeles and New York
SELECT * FROM dbo.RoadPaths
WHERE from_city = 'LAX' AND to_city = 'JFK';
GO
-- Listing 9-43: Creation Script for the fn_RoadsTC UDF
IF OBJECT_ID('dbo.fn_RoadsTC') IS NOT NULL
DROP FUNCTION dbo.fn_RoadsTC;
GO
CREATE FUNCTION dbo.fn_RoadsTC() RETURNS @RoadsTC TABLE
(
uniquifier INT NOT NULL IDENTITY,
from_city VARCHAR(3) NOT NULL,
to_city VARCHAR(3) NOT NULL,
distance INT NOT NULL,
route VARCHAR(MAX) NOT NULL,
PRIMARY KEY (from_city, to_city, uniquifier)
)
AS
BEGIN
DECLARE @added AS INT;
INSERT INTO @RoadsTC
SELECT city1 AS from_city, city2 AS to_city, distance,
'.' + city1 + '.' + city2 + '.'
FROM dbo.Roads;
SET @added = @@rowcount;
INSERT INTO @RoadsTC
SELECT city2, city1, distance, '.' + city2 + '.' + city1 + '.'
FROM dbo.Roads;
SET @added = @added + @@rowcount;
