在SELECT中重复使用别名 [英] reusing alias in SELECT

问题描述

我想要做的是添加另一个列计算（cr - dr）

What I am trying to do is add another column that calculates (cr - dr)

看到你不能在SELECT子句中重复使用别名，

Seeing as you cannot re-use an alias inside a SELECT clause, how would you go about calculatin total

    SELECT SUM(b.bet_win * cy.fx_rate )as dr, SUM(b.bet_loss * cy.fx_rate ) as cr, cr+dr as total
    FROM ....
    WHERE ....

推荐答案

在SQL Server或Oracle中，我会使用CTE，使用MySQL，您将使用一个子查询：

In SQL Server or Oracle, I'd use a CTE, but since you're using MySQL, you'd use a subquery:

SELECT dr, cr, cr + dr as total 
FROM (
    SELECT 
         SUM(b.bet_win * cy.fx_rate ) as dr, 
         SUM(b.bet_loss * cy.fx_rate ) as cr
    FROM ....
    WHERE ....) t;

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