1、查找表中多餘的重覆記錄，重覆記錄是根據單個欄位（peopleId）來判斷 select * from peoplewhere peopleId in (select peopleId from people group by peopleId having count (peopleId) > ...
1、查找表中多餘的重覆記錄，重覆記錄是根據單個欄位（peopleId）來判斷
select * from peoplewhere peopleId in (select peopleId from people group by peopleId having count (peopleId) > 1)
2、刪除表中多餘的重覆記錄，重覆記錄是根據單個欄位（peopleId）來判斷，只留有rowid最小的記錄
where peopleId in (select peopleId from people group by peopleId having count (peopleId) > 1)
and rowid not in (select min(rowid) from people group by peopleId having count (peopleId)>1)
3、查找表中多餘的重覆記錄（多個欄位）
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、刪除表中多餘的重覆記錄（多個欄位），只留有rowid最小的記錄
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
5、查找表中多餘的重覆記錄（多個欄位），不包含rowid最小的記錄
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq havingcount(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
(二)
比方說 在A表中存在一個欄位“name”，而且不同記錄之間的“name”值有可能會相同，現在就是需要查詢出在該表中的各記錄之間，“name”值存在重覆的項；
如果還查性別也相同大則如下:
(三)
方法一
declare cur_rows cursor local for select 主欄位,count(*) from 表名 group by 主欄位 having
count(*) >； 1
open cur_rows
fetch cur_rows into @id,@max
while @@fetch_status=0
begin
select @max = @max -1
set rowcount @max
delete from 表名 where 主欄位 = @id
fetch cur_rows into @id,@max
end
close cur_rows
set rowcount 0
方法二
有兩個意義上的重覆記錄，一是完全重覆的記錄，也即所有欄位均重覆的記錄，二是部分關鍵欄位重
復的記錄，比如Name欄位重覆，而其他欄位不一定重覆或都重覆可以忽略。
1、對於第一種重覆，比較容易解決，使用 select distinct * from tableName 就可以得到無重覆記錄的結果集。
如果該表需要刪除重覆的記錄（重覆記錄保留1條），可以按以下方法刪除
select distinct * into #Tmp from tableName drop table tableNameselect * into tableName from #Tmp
drop table #Tmp
發生這種重覆的原因是表設計不周產生的，增加唯一索引列即可解決。
2、這類重覆問題通常要求保留重覆記錄中的第一條記錄，操作方法如下
假設有重覆的欄位為Name,Address，要求得到這兩個欄位唯一的結果集
select identity(int,1,1) as autoID, * into #Tmp from tableNameselect min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID
select * from #Tmp where autoID in(select autoID from #tmp2)
最後一個select即得到了Name，Address不重覆的結果集（但多了一個autoID欄位，實際寫時可以寫在select子句中省去此列）
(四)查詢重覆
select * from tablename where id in (select id from tablename
group by id
having count(id) > 1
)
