Mysql 将查询表中的结果用于另一个查询

共有3个不同的表，从第一个表中我得到了“联系人id”，基于此，我想对下两个表进行求和，然后减去下面代码中的表。
我试图将第一个查询的结果“contact_id”用于以下查询

SELECT (
    SELECT `id`
    FROM `civicrm_contact`
    WHERE `first_name` LIKE 'test2'
) AS contact_id

=============================================================

SELECT (
    SELECT SUM(`total_amount`)
    FROM `civicrm_contribution`
    WHERE `contact_id`=
)
-
(
    SELECT SUM(`fee_amount`)
    FROM `civicrm_participant`
    WHERE `contact_id`= 
) As RemainingPoints

---

您需要使用子查询：

SELECT (
    SELECT SUM(`total_amount`)
    FROM `civicrm_contribution`
    WHERE `contact_id`= (SELECT `id` FROM `civicrm_contact` WHERE `first_name` LIKE 'test2' ) AS contact_id) 
)
-
(
    SELECT SUM(`fee_amount`)
    FROM `civicrm_participant`
    WHERE `contact_id`= (SELECT `id` FROM `civicrm_contact` WHERE `first_name` LIKE 'test2' ) AS contact_id)
) As RemainingPoints

---

这将解决您的问题：

SELECT (
    SELECT SUM(`total_amount`)
    FROM `civicrm_contribution`
    WHERE `contact_id` in (SELECT `id` FROM `civicrm_contact` WHERE `first_name` LIKE 'test2' ) AS contact_id) 
)
-
(
    SELECT SUM(`fee_amount`)
    FROM `civicrm_participant`
    WHERE `contact_id` in (SELECT `id` FROM `civicrm_contact` WHERE `first_name` LIKE 'test2' ) AS contact_id)
) As RemainingPoints

---

您应该将子查询的结果限制为1，否则将导致错误，最好的方法是使用

'='

而不是

'like'

匹配名称

SELECT (
    SELECT SUM(`total_amount`)
    FROM `civicrm_contribution`
    WHERE `contact_id`= (SELECT `id` FROM `civicrm_contact` WHERE `first_name` LIKE 'test2' limit 1 ) AS contact_id) 
)
-
(
    SELECT SUM(`fee_amount`)
    FROM `civicrm_participant`
    WHERE `contact_id`= (SELECT `id` FROM `civicrm_contact` WHERE `first_name` LIKE 'test2' limit 1 ) AS contact_id)
) As RemainingPoints

这可以帮助你

SELECT @s:=1+1 ,@s + 4,@s-1

o/p-@s:=1+1 |@s+4 |@s-1

       2  |    6|   1

---

查询可能会失败，因为内部子查询可能返回多个值。在中使用

而不是
=
在这种情况下，让我们使用限制1。感谢您详细的回答！我最终改变了结构，并在查询中使用了sub-select。谢谢你的明确提示，我不知道。