sql - 查询末尾的 (+) 是什么？

Question

这个问题在这里已经有了答案:





Oracle "(+)" Operator

(4 个回答)



How to find LEFT OUTER JOIN or RIGHT OUTER JOIN with ORACLE JOIN (+)

(2 个回答)


6年前关闭。




我对 oracle sql 很陌生，刚遇到一个看起来像这样的查询

SELECT some_field
FROM some_table
WHERE some_other_field=some_value(+);

我对代码进行了简化和 annonimized，但我很好奇 (+) 是什么？在末尾。我不记得在 mssql 世界中看到过。

Answer 1

这是 Oracle 旧的外连接语法:

To write a query that performs an outer join of tables A and B and returns all rows from A (a left outer join), use the LEFT [OUTER] JOIN syntax in the FROM clause, or apply the outer join operator (+) to all columns of B in the join condition in the WHERE clause. For all rows in A that have no matching rows in B, Oracle Database returns null for any select list expressions containing columns of B.

http://docs.oracle.com/cd/B19306_01/server.102/b14200/queries006.htm