hive常用命令

啟動hive：
start-all.sh
hive

進入hive之後，創建一個hive資料庫庫：
create database if not exists db;

創建一個新表，結構與其他一樣
hive> create table new_table like records;

創建分區表：
hive> create table logs(ts bigint,line string) partitioned by (dt String,country String);

載入分區表數據：
hive> load data local inpath '/home/hive/partitions/files' into table logs partition (dt='2017-08-01',country='GB');

展示表中有多少分區：
hive> show partitions logs;

展示所有表：
hive> show tables;
lists all the tables
hive> show tables '.*s';

顯示表的結構信息
hive> DESCRIBE invites;
shows the list of columns

更新表的名稱：
hive> ALTER TABLE source RENAME TO target;

添加新一列
hive> ALTER TABLE invites ADD COLUMNS (new_col2 INT COMMENT 'a comment');

刪除表：
hive> DROP TABLE records;
刪除表中數據，但要保持表的結構定義
hive> dfs -rmr /user/hive/warehouse/records;

從本地文件載入數據：
hive> LOAD DATA LOCAL INPATH '/home/hadoop/input/ncdc/micro-tab/sample.txt' OVERWRITE INTO TABLE records;

顯示所有函數：
hive> show functions;

查看函數用法：
hive> describe function substr;

查看數組、map、結構
hive> select col1[0],col2['b'],col3.c from complex;

內連接：
hive> SELECT sales.*, things.* FROM sales JOIN things ON (sales.id = things.id);

查看hive為某個查詢使用多少個MapReduce作業
hive> Explain SELECT sales.*, things.* FROM sales JOIN things ON (sales.id = things.id);

外連接：
hive> SELECT sales.*, things.* FROM sales LEFT OUTER JOIN things ON (sales.id = things.id);
hive> SELECT sales.*, things.* FROM sales RIGHT OUTER JOIN things ON (sales.id = things.id);
hive> SELECT sales.*, things.* FROM sales FULL OUTER JOIN things ON (sales.id = things.id);

in查詢：Hive不支持，但可以使用LEFT SEMI JOIN
hive> SELECT * FROM things LEFT SEMI JOIN sales ON (sales.id = things.id);

Map連接：Hive可以把較小的表放入每個Mapper的記憶體來執行連接操作
hive> SELECT /*+ MAPJOIN(things) */ sales.*, things.* FROM sales JOIN things ON (sales.id = things.id);

INSERT OVERWRITE TABLE ..SELECT：新表預先存在
hive> FROM records2
> INSERT OVERWRITE TABLE stations_by_year SELECT year, COUNT(DISTINCT station) GROUP BY year
> INSERT OVERWRITE TABLE records_by_year SELECT year, COUNT(1) GROUP BY year
> INSERT OVERWRITE TABLE good_records_by_year SELECT year, COUNT(1) WHERE temperature != 9999 AND (quality = 0 OR quality = 1 OR quality = 4 OR quality = 5 OR quality = 9) GROUP BY year;

CREATE TABLE ... AS SELECT：新表表預先不存在
hive>CREATE TABLE target AS SELECT col1,col2 FROM source;