mysql 各种级联查询后更新（update select）.

CREATE TABLE `tb1` (

`id` int(11) NOT NULL,

`A` varchar(100) default NULL,

`B` varchar(100) default NULL,

`C` varchar(20) default NULL,

PRIMARY KEY (`id`),

KEY `id` (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=latin1;

CREATE TABLE `tb2` (

`id` int(11) NOT NULL,

`A` varchar(100) default NULL,

`B` varchar(100) default NULL,

PRIMARY KEY (`id`),

KEY `id` (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=latin1;

级联更新1：

update tb1,

tb2

set tb1.a=tb2.a,tb1.b=tb2.b

where tb1.id=tb2.id

级联更新2：

update tb1,

(select * from tb2) as tb2

set tb1.a=tb2.a,tb1.b=tb2.b

where tb1.id=tb2.id

级联更新3：

update (select * from tb1 group by C) as temp,

       tb2,

       tb1

set tb1.a = tb2.a,

    tb1.b = tb2.b

where tb1.id = tb2.id and

      temp.id = tb2.id

级联更新4：

update tb1 left join tb2 on tb1.id = tb2.id

set tb1.a = tb2.a,

tb1.b = tb2.b

where ......