for example:
select * from 表A a, 表B b where a.name = b.name(+);a.name = b.name(+) means:
"table B" is a supplementary matching table, that is, there is no matching record in table B, and table A is also queried, which is equivalent to a left join (left join), namely:
a. name(+)=b.name is equivalent to b left join a on a.name=b.name
a.name=b.name(+) is equivalent to a left join b on a.name=b.name
Notice:
The (+) operator can only appear in the where clause and cannot be used with the outer join syntax
When using the (+) operator to perform an outer join, if multiple conditions are included in the where clause, the (+) operator must be included in all conditions.
The (+) operator only works on columns, not on expressions.
The (+) operator cannot be used with the or and in operators.
The (+) operator can only be used to implement left and right outer joins, not full outer joins.