(+) is a join.
For example
, SELECT a.*, b.* from a(+) = b is a right join, which is equivalent to select a.*, b.* from a right join b
SELECT a.*, b.* from a = b(+) is a left join, which is equivalent to select a.*, b.* from a left join b
, that is, the other side of the "(+)" location is the direction of the connection, usually the full set and the partial set are combined. When connecting, put a (+) behind the columns of the partial collection to achieve the effect of showing a null when there is no match
For example
, SELECT a.*, b.* from a(+) = b is a right join, which is equivalent to select a.*, b.* from a right join b
SELECT a.*, b.* from a = b(+) is a left join, which is equivalent to select a.*, b.* from a left join b
, that is, the other side of the "(+)" location is the direction of the connection, usually the full set and the partial set are combined. When connecting, put a (+) behind the columns of the partial collection to achieve the effect of showing a null when there is no match