MySQL：如何将当前 select 语句中创建的两个字段的结果相加？

Posted 2023-02-26

【中文标题】MySQL：如何将当前 select 语句中创建的两个字段的结果相加？

【英文标题】：MySQL: How to add the result of two fields created in the current select statement?

【发布时间】：2011-06-29 16:34:54

【问题描述】：

我正在创建一个 mysql 视图表，所以到目前为止我的代码看起来像这样：

CREATE VIEW `myview`
AS SELECT
    (do some stuff here) AS `Revenue1`,
    (do some more here)  AS `Revenue2`
FROM ...

现在我想添加一个列是这两个字段的总和，所以我尝试了这个：

CREATE VIEW `myview`
AS SELECT
    (do some stuff here) AS `Revenue1`,
    (do some more here)  AS `Revenue2`,
    (`Revenue1` + `Revenue2`) AS `TotalRevenue`
FROM ...

但这会导致错误提示 Revenue1 字段未知。如何添加这两个字段并将结果作为新列获取？

【参考方案1】：

你必须重复以下内容：

CREATE VIEW `myview`
AS SELECT
    (do some stuff here) AS `Revenue1`,
    (do some more here)  AS `Revenue2`,
    ((do some stuff here) + (do some more here)) AS `TotalRevenue`
FROM ...

或创建第二个视图：

CREATE VIEW `myview_Two`
AS SELECT
    `Revenue1`,
    `Revenue2`,
    `Revenue1` + `Revenue2` AS `TotalRevenue`
FROM myview

【参考方案2】：

我认为这应该可行：

CREATE VIEW `myview` 
AS 
  SELECT 
       (do some stuff here) AS `Revenue1`,     
       (do some more here)  AS `Revenue2`,     
       (do some stuff here) + (do some more here) AS `TotalRevenue`
  FROM ... 

【讨论】：

看到这个***.com/questions/206062/…

你每天都会学到新东西。答案已更新.. 虽然必须有更好的方法来做到这一点......