Question

SELECT date_uploaded,
       (SELECT CAST(tablename.date_uploaded AS date) AS Expr1) AS newdate
  FROM tablename

我的问题是，如何GROUP BY给出新的虚拟列（Expr1）？

Answer 1

在大多数数据库中，您需要在group by：

中重复该条件

SELECT date_uploaded, CAST(tablename.date_uploaded AS date) AS newdate
FROM tablename
GROUP BY CAST(tablename.date_uploaded AS date);

对于简单的表达式，完全没有嵌套的SELECT。我不知道人们在哪里学会做这些事情，但我在过去看过类似的例子。

Answer 2

最简单的方法：

SELECT * FROM
(

        SELECT date_uploaded,
        (SELECT CAST(tablename.date_uploaded AS date) AS Expr1) AS newdate
        FROM tablename

 )AS TB  

GROUP BY TB.newdate

如何使用多个select语句对新表达式进行分组

2 个答案: