[英]Self-join of a subquery
我想知道,是否有可能使用PostgreSQL加入查詢結果?
您可以使用WITH:
WITH subquery AS(
SELECT * FROM TheTable
)
SELECT *
FROM subquery q1
JOIN subquery q2 on ...
或者通過創建包含查詢的VIEW,並加入:
SELECT *
FROM TheView v1
JOIN TheView v2 on ...
或蠻力方法:鍵入子查詢兩次:
SELECT *
FROM (
SELECT * FROM TheTable
) sub1
LEFT JOIN (
SELECT * FROM TheTable
) sub2 ON ...
你的意思是,對表的查詢結果,對同一個表。 如果是,那么是的,這是可能的......例如
--Bit of a contrived example but...
SELECT *
FROM Table
INNER JOIN
(
SELECT
UserID, Max(Login) as LastLogin
FROM
Table
WHERE
UserGroup = 'SomeGroup'
GROUP BY
UserID
) foo
ON Table.UserID = Foo.UserID AND Table.Login = Foo.LastLogin
是的,只需查詢別名:
SELECT *
FROM (
SELECT *
FROM table
) t1
JOIN (
SELECT *
FROM table
) t2
ON t1.column < t2.other_column
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