现在有表
Blog日志表
字段如下:
id,kindid,newuseridBlogKind个人日志分类表
字段如下
kindid,newuserid,blogNum
我要求出Blog表中的记录和,如用户newuserid=10000,kindid=10 的count(id)=10
更新到BlogKind表中,条件是Blog.kindid=BlogKind.kindid and Blog.newuserid = BlogKind.newuserid
如果条件不满足就不操作
我现在的SQL:
update blogkind set blognum = (select count (1) from blog where newuserid = blogkind.newuserid and kindid = blogkind.kindid)
全部更新掉了。数据不合理,在BlogKind中的有些记录BlogNum为0了
Blog日志表
字段如下:
id,kindid,newuseridBlogKind个人日志分类表
字段如下
kindid,newuserid,blogNum
我要求出Blog表中的记录和,如用户newuserid=10000,kindid=10 的count(id)=10
更新到BlogKind表中,条件是Blog.kindid=BlogKind.kindid and Blog.newuserid = BlogKind.newuserid
如果条件不满足就不操作
我现在的SQL:
update blogkind set blognum = (select count (1) from blog where newuserid = blogkind.newuserid and kindid = blogkind.kindid)
全部更新掉了。数据不合理,在BlogKind中的有些记录BlogNum为0了
应该条件还差if exists(),我应该还差一步就可以了。望你能点一下!
update blogkind
set blognum = (select count (1) from blog where newuserid = blogkind.newuserid and kindid = blogkind.kindid)
where ......
set blognum = (select count(1) from blog where newuserid = blogkind.newuserid and kindid = blogkind.kindid)
from blog
where blog.newuserid = blogkind.newuserid and blog.kindid = blogkind.kindid
我最主要想了解那个if exists中是怎么写的