Question

我想减去同一表中的行（where子句不同）。

SELECT SUM(`balance`) AS `balance` FROM `vouchers`  WHERE `type`='CP' AND `post_status`='yes' GROUP BY `interactive_person`;

上面的查询为我提供了一些理想的结果！第二个查询是

SELECT SUM(`balance`) AS `balance` FROM `vouchers`  WHERE `type`='CR' AND `post_status`='yes' GROUP BY `interactive_person`;

这些查询返回的行多于交互人分组，我希望它减去交互人（是数字）相同但类型改变的记录。简而言之，它就像CashReceipt-CashPayment。我将第一个查询用作第二个查询的子查询，但错误显示该子查询返回的行多。我需要帮助解决这个问题！

Answer 1

您可以使用case在同一查询中计算sum()

SELECT 
SUM(CASE WHEN `type`='CP' THEN `balance` ELSE 0 END) AS CP_balance,
SUM(CASE WHEN `type`='CR' THEN `balance` ELSE 0 END) AS CR_balance,
SUM(CASE WHEN `type`='CP' THEN `balance` WHEN `type`='CR' THEN  -1 * `balance` ELSE 0 END) AS diff
FROM `vouchers`  
WHERE `post_status`='yes' 
GROUP BY `interactive_person`;

如何减去类型不同的行的同一列？

1 个答案: