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)。无论如何都要在一个声明中做到这一点吗？

Answer 1

你可以UNION ALL他们不要使用UNION，因为它会忽略重复值（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

您可以在不使用此类

的情况下执行此操作

示例查询

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) 
)

Answer 3

您可以使用UNION和子选择来执行此操作：

select sum(`sum`) FROM
(
  select sum(field_one) as `sum` from t_a join t_b on (t_a.bid = t_b.id) where t_b.user_id=:id
  UNION ALL
  select sum(field_two) from t_c join t_d on (t_c.did = t_d.id) where t_d.user_id=:id
  UNION ALL
  select sum(field_three) from t_e where t_e.user_id=:id
) as x;

编辑：根据Peter Lang的建议，更新了我使用UNION ALL的答案。

添加多个SQL选择的结果？

3 个答案: