What is outer join in database?

FULL OUTER JOIN:

Another type of join is called a SQL Server FULL OUTER JOIN. This type of join returns all rows from the LEFT-hand table and RIGHT-hand table with nulls in place where the join condition is not met.

Syntax:

The syntax for the FULL OUTER JOIN in SQL Server (Transact-SQL) is:

SELECT columns
FROM table1
FULL [OUTER] JOIN table2
ON table1.column = table2.column;