如何选择总和（列）的所有列行

Question

select p_id,paid_amount,date, from payments

这是我的查询，它工作正常，但当我添加总和列时，它只选择第一行。

select p_id,paid_amount,date,sum(paid_amount) as 'sum' from payments

Answer 1

Most DBMSes support Windowed Aggregates, then it's a simple

select p_id,paid_amount,date,
  sum(paid_amount) over () as "sum" 
from payments

Otherwise you can use a Scalar Subquery:

select p_id,paid_amount,date,
  (select sum(paid_amount) from payments) as "sum"
from payments

Answer 2

进行两次查询。

SELECT p_id,paid_amount,date, FROM payments;
SELECT SUM(paid_amount) FROM payments;