One of the database interview series: internal and external connections

An inner join is a tuple that returns a relationship table that satisfies both the query condition and the join condition

An outer join is a tuple that returns a relationship table that satisfies the query criteria but does not necessarily meet the join criteria

Outer connection: Left outer connection, right outer connection, full outer connection

A LEFT outer join is a tuple that returns the left table that satisfies the query condition but does not necessarily meet the join criteria

A right outer join is a tuple that returns the right table that satisfies the query criteria but does not necessarily meet the join criteria

A full outer join is a tuple that returns the left table that satisfies the query criteria and satisfies the query criteria on the right

Here are two basic tables: S table and SC table

The results of the inner join return are as follows:

The results returned by left join are as follows:

The right connection returns the following results:

The results of the full outer join return are as follows:

One of the database interview series: internal and external connections