如何在单个查询中组合这两个查询

Question

如何将这两个查询合并为单个查询

1。 select sum(amount) as received from voucher where amount>0

2。 select sum(amount) as repaid from voucher where amount<0

Answer 1

您可以使用条件聚合

select sum( case when amount > 0 then amount else 0 end ) as received,
       sum( case when amount < 0 then amount else 0 end ) as repaid 
FROM t

您可以在Postgres 9.4 +

中使用FILTER

select sum( amount ) filter (where  amount > 0 ) as received,
       sum( amount ) filter (where  amount < 0 ) as repaid 
FROM t

Answer 2

试试这个。，

select case when amount>0 then sum(amount) end as 'received', 
case when amount<0 then sum(amount) end as 'repaid' from voucher