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Mysql实现全连接FULL OUTER JOIN

2012-05-15 22:00 288 查看
http://dev.mysql.com/doc/refman/5.5/en/join.html

You can emulate FULL OUTER JOIN using UNION (from MySQL 4.0.0 on):

with two tables t1, t2:

SELECT * FROM t1

LEFT JOIN t2 ON t1.id = t2.id

UNION

SELECT * FROM t1

RIGHT JOIN t2 ON t1.id = t2.id

with three tables t1, t2, t3:

SELECT * FROM t1

LEFT JOIN t2 ON t1.id = t2.id

LEFT JOIN t3 ON t2.id = t3.id

UNION

SELECT * FROM t1

RIGHT JOIN t2 ON t1.id = t2.id

LEFT JOIN t3 ON t2.id = t3.id

UNION

SELECT * FROM t1

RIGHT JOIN t2 ON t1.id = t2.id

RIGHT JOIN t3 ON t2.id = t3.id
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