What does (+) in Oracle mean

oracle Medium (+) What does that mean?

Concept elaboration oracle Medium （+） It's a special usage ,（+） Indicates external connection , And always on the side of the non main table .

For example, left outer connection ：
select A.a,B.a from A LEFT JOIN B ON A.b=B.b;
Equivalent to
select A.a,B.a from A,B where A.b = B.b(+);

Another example , This is the right outer connection ：
select A.a,B.a from A RIGHT JOIN B ON A.b=B.b;
Equivalent to
select A.a,B.a from A,B where A.b (+) = B.b;

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