In SQL, a join clause is used to combine columns from one or more tables into a new table). The operation corresponds to a join operation in relational algebra. A join requires each row in the two joined tables to have matching column values, and is a commonly used join operation in applications). There are different types of joins in SQL, including:

• Inner Join: This returns records that have matching values in both tables. Inner join creates a new result table by combining column values of two tables based upon the join-predicate).

• Left (Outer) Join: This returns all records from the left table and the matching rows from the right table. The result is NULL from the right side if there is no match.

• Right (Outer) Join: This returns all records from the right table and the matching rows from the left table. The result is NULL from the left side when there is no match.

• Full (Outer) Join: This returns all rows from both tables and NULL values where there is no match.

• Cross Join: This combines every row on the left table with every row on the right table.

SQL developers can add joins to their queries to create complex views. The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns. The LEFT JOIN command returns all rows from the left table and the matching rows from the right table. The RIGHT JOIN command returns all rows from the right table and the matching rows from the left table. The FULL OUTER JOIN keyword returns all the rows from both tables.