What are various joins used while writing SUBQUERIES

Self join-Its a join foreign key of a table references the same table. Outer Join–Its a join condition used where One can query all the rows of one of the tables in the join condition even though they don’t satisfy the join condition. Equi-join–Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table.