sql server几种Join的区别测试方法

CREATETABLE CONSUMERS 
(
CONSUMER_ID INTNOTNULL,
CONSUMER_NAME VARCHAR(10) NOTNULL
)
CREATETABLE ORDERS
(
CONSUMER_ID INTNOTNULL, 
ORDER_ID VARCHAR(10) NOTNULL)

INSERT CONSUMERS VALUES ( 1, 'AA')
INSERT CONSUMERS values ( 2, 'BB')
INSERT CONSUMERS values ( 3, 'CC')
INSERT ORDERS VALUES ( 2, 'O100001')
INSERT ORDERS VALUES ( 3, 'O100002')
INSERT ORDERS VALUES ( 3, 'O100003')
INSERT ORDERS VALUES ( 4, 'O100004')

--Inner Join
--筛选两边都有的记录
SELECT *
FROM ORDERS o INNER JOIN CONSUMERS c
ON o.CONSUMER_ID = c.CONSUMER_ID
--Full Out Join
--两边都筛选出来，匹配能匹配的，不能匹配的用NULL列出
SELECT *
FROM ORDERS o FULL OUTER JOIN CONSUMERS c
ON o.CONSUMER_ID = c.CONSUMER_ID
--Cross Join
--列出两边所有组合，即笛卡尔集A×B
SELECT *
FROM ORDERS o CROSS JOIN CONSUMERS c
--Left Join
--以左边的表为主表，列出主表所有记录，匹配能匹配的，不能匹配的用NULL列出
SELECT * 
FROM CONSUMERS c left join ORDERS o
on c .CONSUMER_ID = o .CONSUMER_ID
--Right Join
--以右边的表为主表，列出主表所有记录，匹配能匹配的，不能匹配的用NULL列出
SELECT * 
FROM CONSUMERS c RIGHT JOIN ORDERS o
on c .CONSUMER_ID = o .CONSUMER_ID