SQL语句中的判断语句

Question

有下面一个SQL：
select * from table_a a_
left outer join table_b b_ on a_.ins_id = b_.id
where (b_.state="ok" or b_.state="error") and b_.date>now()
问题是：
当b_.state="ok"时 b_.date>now()
当b_.state="error"时b_.date>a_.date

这些条件能不能在一个SQL中实现!

数据库为MySql 5.1

Answer 1

where (b_.state="ok" and b_.date>now() ) or ( b_.state="error" and b_.date>a_.date )