如何在单独的列中合并多个选择语句？

尝试通过子查询

select count (distinct vid) as SUM_OF_SEC ,(select sum (amount*paidperitem) from pdalis where pid = 501 ;) AS SUM_OF_A , (select sum(amount * paidperitem) from pdalis where pid IN (500,504);) as SUM_OF_P  from pdalis where pid in(500,504);