[英]SQL Select 2 columns as list from single row
我有一個表,其列為[From], [To]
。 我需要將這些列選擇為單個列表,並以此方式進行操作:
SELECT [From] FROM [TableX] WHERE (...)
UNION
SELECT [To] FROM [TableX] WHERE (...)
問題是我不想復制WHERE (...)
條件,因為它很長。 有辦法避免這種重復嗎?
使用CTE來防止重復您的WHERE
條件:
;WITH [CTE_Criteria] AS (
SELECT [From], [To]
FROM [TableX]
WHERE (...)
)
SELECT [From] FROM [CTE_Criteria]
UNION
SELECT [To] FROM [CTE_Criteria];
在派生表中執行UNION
,並具有一個公共WHERE
子句。
select *
from
(
SELECT [From] FROM [TableX]
UNION
SELECT [To] FROM [TableX]
)
WHERE (...)
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