我想做这样的事情:
select
case when (select count(*) as score from users t1 ) >5 THEN score else 0 end
当我尝试时出现错误:
column score doesn't exists.
我可以用其他方式做到这一点吗?我需要它来设置一个 LIMIT 值。我当然想这样做:
select
case when (select count(*) as score from users t1 ) >5 THEN (select count(*) as score from users) else 0 end
但我需要执行两次相同的查询。 有人有想法吗?
最佳答案
您可以使用 WITH
子句:
with a as (select count(*) score from t)
select case when score > 5 then score else 0 end from a;
或子查询(内联 View ):
select case when score > 5 then score else 0 end
from (select count(*) score from t) t;
关于PostgreSQL:使用别名列时的情况,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17265151/