sql-server - 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：

消息 207，级别 16，状态 1，第 7 行无效的列名称“文字”。

我尝试了这个，结果相同：

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

Answer 1

当你想要一个派生表时，你需要GROUP BY一个UNION：

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

演示

Answer 2

你可以用c...

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