mysql - 有没有更简单的方法来编写这个查询？

Question

我在 MySQL 中有一个查询执行一些身份验证检查，但它很长。我想知道是否有另一种方法可以缩短/简化它，但实际上所有子句都是必需的。

select nickname from nicknames where nickname = '$nick' and password = '$md5pass' 
union 
select '$nick' as nickname from nicknames AS t1 where not 
  (nickname = '$nick' and password = '$md5pass') 
and not exists 
  (select 1 from nicknames where nickname = '$nick')

Answer 1

这个怎么样？

select coalesce(max(nickname), '$nick')
from nicknames
where nickname = '$nick' and password = '$md5pass';