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.