An inner join is a join in which the values in the columns being joined are compared using a comparison operator.
In the ISO standard, inner joins can be specified in either the FROM or WHERE clause. This is the only type of join that ISO supports in the WHERE clause. Inner joins specified in the WHERE clause are known as old-style inner joins.
This inner join is known as an equi-join. It returns all the columns in both tables, and returns only the rows for which there is an equal value in the join column.