mysql update select用法实例

mysql update select用法实例

mysql update select用法实例

应该使用inner join,即:

UPDATE friends INNER JOIN users ON friends.friendid=users.userid SET friends.friendname=users.username

MySQL是通过临时表来实现FROM子句里面的嵌套查询,那么把嵌套查询装进另外一个嵌套查询里,可使FROM子句查询和保存都是在临时表里进行,然后间接地在外围查询被引用。

我们来看如下sql语句:

update apples

set price = (

select price from (

select * from apples

) as x

where variety = 'gala')

where variety = 'fuji';

继续来看如下两条实例

update a set a.xx= (select yy from b) where a.id = b.id ;

但是在mysql中,不能直接使用set select的结果,必须使用inner join:

update a inner join (select yy from b) c on a.id =b.id set a.xx = c.yy

如下一条经典Mysql update语句赋值嵌套select实例

update mem_player set `DataWarehouse`=(select `DataWarehouse` from (select * from mem_player) as b where `Pid`=100000)

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