" (+)="Oracle SQL中的where子句中的运算符 [英] " (+) = " operator in oracle sql in where clause

问题描述

在更改存储过程时，我遇到了(+)=运算符.我已阅读 Oracle的(+)"运算符，但似乎我的问题与该链接中提到的问题略有不同. 因此，任何人都可以帮助我理解以下声明:

while changing stored procedure i came across (+) = operator. I have read Oracle "(+)" Operator but seems like my problem is slightly different than one mentioned in that link. So, can anyone please help me understand statement like:

select ....
from emp, dept 
where emp.dept_id (+) = dept.dept_id

为什么在使用此条件时他们同时使用+和=符号?如果有人可以帮助我提供示例或链接，让我可以阅读有关此类运算符的信息，我将不胜感激.

why would they use both + and = sign while using this condition? I would be thankful if someone will help me with example or link where i can read about such operators.

推荐答案

这是LEFT OUTER JOIN的不赞成使用的表示法.

This is the deprecated notation of a LEFT OUTER JOIN.

根据ANSI标准的新的首选符号是:

The new and preferred notation according to the ANSI standard is:

select ....
from emp
left outer join dept 
on emp.dept_id = dept.dept_id

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