mysql - 从两个不相关的 MySQL 查询中添加总计

Question

我正在努力找出正确的 MySQL 语法来添加两个查询的结果。查询从表中提取通话记录，都生成单个图形结果，我需要将它们加在一起。我确信这可以通过子查询来完成，但我似乎无法获得正确的语法。

查询如下:

SELECT SUM(costres) - SUM(costadmin)
FROM call_history, client
WHERE MONTH(start) = 3 AND YEAR(start) = 2012
  AND call_history.client_reseller_id = client.id
  AND client.charging_identifier <> 100000
  AND client.charging_identifier <> 999999;

SELECT SUM(costcl) - SUM(costadmin)
FROM call_history, client
WHERE MONTH(start) = 3 AND YEAR(start) = 2012
 AND call_history.client_reseller_id = client.id
 AND client.charging_identifier = 100000
 AND client.charging_identifier <> 999999;

正如我所说，我知道这很简单，但我似乎无法理解 MySQL 中的子查询语法!

提前致谢

乔治

Answer 1

怎么样-

SELECT
    (SUM(IF(client.charging_identifier = 100000, costcl, 0)) - SUM(IF(client.charging_identifier = 100000, costadmin, 0))) +
    (SUM(IF(client.charging_identifier <> 100000, costres, 0)) - SUM(IF(client.charging_identifier <> 100000, costadmin, 0)))
FROM call_history, client
WHERE MONTH(start) = 3 AND YEAR(start) = 2012
AND call_history.client_reseller_id = client.id
AND client.charging_identifier <> 999999;