不同 CTE 上的 UNION

Question

是否可以联合两个独立的 CTE？假设我有以下 2 个查询集：

;WITH [fu] AS (SELECT 1 AS [data]),
[bar] AS (SELECT 5 AS [data])
SELECT a.[data] AS [Val1], b.[data] AS [Val2], (a.[data] + b.[data]) AS [Math] 
FROM [fu] a JOIN [bar] b ON 1=1

;WITH [fu] AS (SELECT 3 AS [data]),
[bar] AS (SELECT 8 AS [data])
SELECT a.[data] AS [Val1], b.[data] AS [Val2], (a.[data] + b.[data]) AS [Math] 
FROM [fu] a JOIN [bar] b ON 1=1

我想要每个 CTE 的不同 [data] 值以及它们在同一记录中的总和。在 CTE 之间放置 UNION 失败（SQL Server 2014 Developer）。是否有有效的 SQL 可以将两个 CTE 作为同一（在本例中为 2 行）记录集的一部分输出？

Answer 1

为什么不简单地将 CTE 转换为子查询？

SELECT ... -- your final logic goes here
FROM (
    SELECT 
        a.[data] AS [Val1], 
        b.[data] AS [Val2], 
        (a.[data] + b.[data]) AS [Math] 
    FROM (SELECT 1 AS [data]) a 
    JOIN (SELECT 5 AS [data]) b ON 1=1
    UNION ALL
    SELECT 
        a.[data] AS [Val1], 
        b.[data] AS [Val2], 
        (a.[data] + b.[data]) AS [Math] 
    FROM (SELECT 3 AS [data]) a 
    JOIN (SELECT 8 AS [data]) b ON 1=1
) t

否则需要先声明所有的CTE，然后在union中使用。这意味着您不能为两个不同的查询重复使用相同的 CTE 别名两次，因此：

WITH 
    [fu1] AS (SELECT 1 AS [data]),
    [bar1] AS (SELECT 5 AS [data]),
    [fu2] AS (SELECT 3 AS [data]),
    [bar2] AS (SELECT 8 AS [data])
SELECT ... -- your final logic goes here    
FROM (
    SELECT 
        a.[data] AS [Val1], 
        b.[data] AS [Val2], 
        (a.[data] + b.[data]) AS [Math] 
    FROM [fu1] a 
    JOIN [bar1] b ON 1=1
    UNION ALL
    SELECT 
        a.[data] AS [Val1], 
        b.[data] AS [Val2], 
        (a.[data] + b.[data]) AS [Math] 
    FROM [fu2] a 
    JOIN [bar2] b ON 1=1
) t

Answer 2

我应该更清楚一点，我最初的挑战是获取一些查询对（在我的示例中为 1 对，每个查询对生成一个数据点），将它们组合成单个记录，然后添加第三个字段关于这两个数据字段的一些数学运算。从那里我需要将单条记录 data/math 记录联合到一个结果集中。使用 CTE 绝对是正确的轨道，但感谢 HABO 的想法，它给了我我需要的 SQL..

;WITH [fu_1] AS (SELECT 1 AS [data]),
[bar_1] AS (SELECT 5 AS [data]),
[fu_2] AS (SELECT 3 AS [data]),
[bar_2] AS (SELECT 8 AS [data])
SELECT a.[data] AS [Val1], b.[data] AS [Val2], (a.[data] + b.[data]) AS [Math] 
FROM [fu_1] a JOIN [bar_1] b ON 1=1
UNION
SELECT a.[data] AS [Val1], b.[data] AS [Val2], (a.[data] + b.[data]) AS [Math] 
FROM [fu_2] a JOIN [bar_2] b ON 1=1

不同 CTE 上的 UNION

UNION on Different CTEs

sql

tsql

union

join

common-table-expression