用CTE订购联合结果

Question

当我有几个CTE后跟UNION of SELECT时，如何使用ORDER BY。我的查询是这样的：

WITH
cte1 AS (SELECT * FROM table1),
cte2 AS (SELECT * FROM table2),
cte3 AS (SELECT * FROM table3)
SELECT cte1.column1,cte1.column2 FROM cte1
UNION
SELECT cte2.column1,cte2.column2 FROM cte2
UNION
SELECT cte3.column1,cte3.column2 FROM cte3

我需要按column1对结果进行排序，其中所有CTE都是整数。

Answer 1

只需添加order by：

即可

WITH cte1 AS (SELECT * FROM table1),
cte2 AS (SELECT * FROM table2),
cte3 AS (SELECT * FROM table3)
SELECT cte1.column1,cte1.column2 FROM cte1
UNION
SELECT cte2.column1,cte2.column2 FROM cte2
UNION
SELECT cte3.column1,cte3.column2 FROM cte3
order by column1 --<< here

联盟上的order by总是命令完整联合，而不仅仅是最后一次选择。

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顺便说一句：您可能还想了解union和union all之间的区别。如果您知道在个人选择（或不关心）之间没有重复，union all会更快。