mysql - 将查询表的结果用于另一个查询

Question

有 3 个不同的表，从第一个表中我得到“contact_id”，并基于此我想对接下来的 2 个表进行求和，然后减去表，如下面的代码所示。
我正在尝试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

Answer 1

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