MySQL：如果行相等则求和

Question

我想创建一个SQL select-query来选择所有内容，但是当client，thickness和material相同时，它们的值为＆＃39; amount＆＃39;应该加上。

我如何创建这样的查询？

Answer 1

如果我理解正确的话。你可以这样做：

SELECT
    client, 
    thickness,
    material,
    SUM(amount) AS TotalAmount
FROM
    Table1
GROUP BY
    client, 
    thickness,
    material 

Answer 2

如果是同一列

SELECT
   SUM(amount) AS Total
FROM
    Tablename
GROUP BY
    client, 
    thickness,
    material