子查询的自联接 [英] Self-join of a subquery
本文介绍了子查询的自联接的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我想知道,是否可以使用PostgreSQL将查询结果与自身连接?
I was wondering, is it possible to join the result of a query with itself, using PostgreSQL?
推荐答案
使用WITH:
WITH subquery AS(
SELECT * FROM TheTable
)
SELECT *
FROM subquery q1
JOIN subquery q2 on ...
通过创建包含查询的VIEW并加入该查询:
Or by creating a VIEW that contains the query, and joining on that:
SELECT *
FROM TheView v1
JOIN TheView v2 on ...
或者蛮力方法:两次输入子查询:
Or the brute force approach: type the subquery twice:
SELECT *
FROM (
SELECT * FROM TheTable
) sub1
LEFT JOIN (
SELECT * FROM TheTable
) sub2 ON ...
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