如何从mysql中两次select的结果中减去 [英] How to substract from the resut of two selects in mysql

问题描述

我想减去两个数，一个是某个字段的内容，一个是查询结果的总和，我该怎么做?这显示了我想要的，但显然不起作用，怎么办?

I want to substract two numbers, one is the contents of a field, the other is the sum of a query result, how can I do it? this shows what I want, but obviously does not work, how to do it?

SELECT monto FROM programaPago WHERE id=2
 **MINUS**
SELECT SUM( caja.monto ) FROM caja  WHERE caja.programaPago_id =2

推荐答案

试试这个:

SELECT ( programaPago.monto - COALESCE(iTotal.TotalMonto,0)) Result
FROM programaPago LEFT JOIN 
    (SELECT programaPago_id, SUM(monto) as TotalMonto
    FROM caja GROUP BY programaPago_id) as iTotal
        ON programaPago.ID = iTotal.programaPago_id
WHERE programaPago.ID = 2

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