TSQL如何按文字分组？

Question

我将这个问题简化为一个非常简单的形式：

SELECT
'A' AS [Literal]
UNION 
SELECT
'B' AS [Literal]
GROUP BY
[Literal]

我收到消息：

  

Msg 207，Level 16，State 1，Line 7   列名称“文字”无效。

我尝试了同样的结果：

SELECT
t.literal FROM 
(SELECT 'A' AS [Literal]) t
UNION 
SELECT
'B' 
GROUP BY
[Literal]

Answer 1

如果您想要GROUP BY UNION：

，则需要派生表格

SELECT X.[Literal], [Count] = COUNT(*)
FROM(
    SELECT [Literal] = 'A'
    UNION ALL 
    SELECT [Literal] = 'B'
) X
GROUP BY X.[Literal]

Demo

Answer 2

你可以使用cte ...

;WITH cte AS (
 SELECT
 'A' AS [Literal]
 UNION 
 SELECT
 'B' AS [Literal])
SELECT [Literal]
FROM cte
GROUP BY [Literal]