在 SELECT 中重用别名

发布于 2024-11-29 21:25:14 字数 241 浏览 0 评论 0原文

我想做的是添加另一列来计算 (cr - dr)

鉴于您无法在 SELECT 子句中重复使用别名，您将如何计算 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 ....

原文

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

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 ....

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平定天下 2024-12-06 21:25:14

在 SQL Server 或 Oracle 中，我会使用 CTE，但由于您使用的是 MySQL，因此您会使用子查询：

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;

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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雪落纷纷 2024-12-06 21:25:14

编辑：不起作用。见评论。
在这种情况下，使用用户变量更快？

SELECT
  @dr:=SUM(b.bet_win * cy.fx_rate ),
  @cr:=SUM(b.bet_loss * cy.fx_rate ), 
  @cr+@dr as total

EDIT: DOES NOT WORK. See comments.
Isn't using a user variable faster in this case?

SELECT
  @dr:=SUM(b.bet_win * cy.fx_rate ),
  @cr:=SUM(b.bet_loss * cy.fx_rate ), 
  @cr+@dr as total

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半城柳色半声笛 2024-12-06 21:25:14

您可以在“总计”栏中重复计算。

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

You can repeat the calculations in the "total" column.

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

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