Question

一句mysql的sql语句，执行出现错误，原因求助。

两张表。统计数据后，结构更新到wz_blog表中。

sql：
update wz_blog
set wz_blog.comnum = wz_comment.cnum
From (select gid,count(*) AS cnum from wz_comment group by gid) wz_comment
where wz_blog.gid =wz_comment.gid

[Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'From (select gid,count(*) AS cnum from kanwz_comment group by gid) kanwz_comment' at line 3

Answer 1

update 语句后面不可以跟 from 的，你上面的SQL可以这样写
update wz_blog
set wz_blog.comnum =
(select count(*) from wz_comment where wz_comment.gid = wz_blog.gif)
where exists (select 1 from wz_comment where wz_comment.gid = wz_blog.gif)

Answer 2

UPDATE wz_blog, (select gid,count(*) AS cnum from wz_comment group by gid) wz_comment SET wz_blog.comnum=wz_comment.cnum WHERE wz_blog.gid =wz_comment.gid;
你试试看，如果不行再跟我讲

Answer 3

update wz_blog
set comnum=(select count(*) as cnum from wz_comment where wz_blog.gid =wz_comment.gid group by gid)

Answer 4

update
wz_blog
set
wz_blog.comnum = (select count(*) AS cnum from wz_comment where wz_blog.gid = wz_comment.gid);