SQL查询中(+)的含义 [英] Meaning of (+) in SQL queries

问题描述

我在Oracle中遇到了一些包含'(+)'的SQL查询，但我不知道这是什么意思.有人可以解释其目的或提供其使用示例吗? 谢谢

I've come across some SQL queries in Oracle that contain '(+)' and I have no idea what that means. Can someone explain its purpose or provide some examples of its use? Thanks

推荐答案

它是OUTER JOIN的Oracle同义词.

It's Oracle's synonym for OUTER JOIN.

SELECT *
FROM a, b
WHERE b.id(+) = a.id

得到与

SELECT *
FROM a
     LEFT OUTER JOIN b
     ON b.id = a.id

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