用于避免检查空值评估的where子句中的case语句

Question

我有像

这样的查询

case when (
  select sum(amount) 
  from table 
  where id in(10,100) 
    and to_char(month,'YYYY-MM') = to_char(@date::date,'YYYY-MM')
) is null 
then (
  select sum(amount) 
  from table 
  where id in(10,100) 
    and to_char(month,'YYYY-MM') = to_char(@date::date- interval '1 month','YYYY-MM')
)
else (
  select sum(amount) 
  from table 
  where id in(10,100) 
    and to_char(month,'YYYY-MM') = to_char(@date::date,'YYYY-MM')
) end

我只需要重写这个查询，我们可以在postgres的where子句中使用case语句

Answer 1

我认为你想要这样的东西，但不是很清楚。

coalesce(select sum(amount) 
      from table 
      where id in(10,100) 
        and to_char(month,'YYYY-MM') = to_char(@date::date,'YYYY-MM')
    ,
     select sum(amount) 
      from table 
      where id in(10,100) 
        and to_char(month,'YYYY-MM') = to_char(@date::date- interval '1 month','YYYY-MM')
    )