Everyday SQL (6)

这是我工作遇到的问题，从别的组里要来了一堆SQL code，大概是四五年前在那工作的人写的，感觉是old style，之前从没见过，贴出来给大家。

Q: What’s the meaning of (+) in SQL queries (Oracle)?

 

A: It’s Oracle’s synonym for OUTER JOIN.

Example：

 

SELECT *

FROM a, b

WHERE b.id(+) = a.id

 

gives the same result as

 

SELECT *

FROM a

LEFT OUTER JOIN b

ON b.id = a.id

 

Or we can say (+) indicates this side gets nulls when no match can be found.