SQL Server : Combine several SELECT statements with "WITH" part into a UNION

Question

我有几个这样的语句(使用WITH语句):

WITH valDiff AS (SELECT <ComplexClause1> AS v1 FROM [MyTable] WHERE <OtherClause1>) SELECT SUM(CASE WHEN v1 < @MaxVal THEN v1 ELSE @MaxVal END) FROM valDiff

UNION

WITH valDiff AS (SELECT <ComplexClauseN> AS v1 FROM [MyTable] WHERE <OtherClauseN>) SELECT SUM(CASE WHEN v1 < @MaxVal THEN v1 ELSE @MaxVal END) FROM valDiff

我需要将它们合并到一个联合中，以便“一口气”返回结果。这些语句本身工作得很好，但是如果我在它们之间添加单词“UNION”，就像我上面显示的那样，我会收到以下错误:

Incorrect syntax near the keyword 'UNION'.
Incorrect syntax near the keyword 'with'.
If this statement is a common table expression, an xmlnamespaces clause or a change tracking context clause, the previous statement must be terminated with a semicolon."

我做错了什么？

Answer 1

WITH 将跨越 UNION 中的所有子句

;WITH valDiff AS 
(
whatever
) 
SELECT ... FROM valDiff ...
UNION ALL
SELECT ... FROM valDiff ...

每个子句中都有不同的 CTE(如本例所示):

;WITH CTE1 AS 
(
whatever
) , CTE2 AS
(
something
)
SELECT ... FROM CTE1 ...
UNION ALL
SELECT ... FROM CTE2 ...