添加多个SQL选择的结果？

Question

我有三个SQL选择,我需要将其结果加在一起.三个中的两个使用相当复杂的连接.

select sum(field_one) from t_a join t_b on (t_a.bid = t_b.id) where t_b.user_id=:id
select sum(field_two) from t_c join t_d on (t_c.did = t_d.id) where t_d.user_id=:id
select sum(field_three) from t_e where t_e.user_id=:id

我需要的是所有三个值的总和. sum(field_one)+sum(field_two)+sum(field_three).反正有没有在一个声明中这样做？

Answer 1

你可以UNION ALL.
不要使用UNION,因为它省略了重复的值(5+5+5会导致5).

Select Sum(s)
From
(
  Select Sum(field_one) As s ...
  Union All
  Select Sum(field_two) ...
  Union All
  Select Sum(field_three) ...
) x

Answer 2

您无需使用Union即可执行此操作

样品查询

select( (select 15) + (select 10) + (select 20)) 

您的查询

select
(
    (select sum(field_one) from t_a join t_b on (t_a.bid = t_b.id) where t_b.user_id=:id) +
    (select sum(field_two) from t_c join t_d on (t_c.did = t_d.id) where t_d.user_id=:id) +
    (select sum(field_three) from t_e where t_e.user_id=:id) 
)