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## Introduction to `FULL OUTER JOIN`
In **`FULL OUTER JOIN`**, we join two tables' values with a common attribute. The non-matching records are joined with the ```NULL``` value for both tables. 

In `FULL OUTER JOIN`, the following happens:

1. First, an #key# inner join: In inner join, we match two table entries on some matching condition. #key# is performed.
2. Then, the rest of the entries in both tables are joined with ```NULL``` values.



## Syntax
The syntax of the ```FULL OUTER JOIN``` query is as follows:

SELECT column_name(s) FROM table1 
  FULL OUTER JOIN table2 
  ON conditional_expression;

We can better understand this with an example.

## Example
Consider the following tables:

COMPANY

align-center

DEPARTMENT

SELECT EMP_ID, NAME, DEPT FROM COMPANY 
  FULL OUTER JOIN DEPARTMENT
  ON COMPANY.ID = DEPARTMENT.EMP_ID;

## Explanation

The above query will join the values in the `id` column of the COMPANY table with the values of the ```emp_id``` column of the DEPARTMENT table. The rest of the entries in both tables will join with ```NULL``` values.


The above `FULL OUTER JOIN` query will produce the following table.

Result table

postgresql.tar.gz