Full Outer Join in SQL

Last Updated: 22nd June, 2023

Overview

Full Join in SQL is a type of join operation that combines the results of two or more tables. It returns all rows when there is at least one match in either left or right table. It is also known as Full Outer Join. It is used to combine the results of two or more tables, even if there are no matches in the other table.

Definition

Akash is a data analyst working for a large retail company. He was tasked with creating a report that included data from two different tables. The tables contained information about customers and their orders, as well as orders and their respective items. Akash knew that to get the complete picture of the data. He would need to use a full join in SQL. So, he wrote a query, but unfortunately, it was wrong. Let's help him with it.

Full Join in SQL is a type of join operation that returns all rows from the left table and all rows from the right table. It combines the results of two or more tables, even if no matches exist in the other table.

Syntax

The syntax for a full join in SQL is:

SELECT *
FROM table_1
FULL JOIN table_2
ON table_1.column_name=table_2.column_name;

Example

Let's consider two tables, Table A and Table B. Table A contains information about customers and their orders. Table B contains information about orders and their respective items.

We can use a full join in SQL to join these two tables together. Here is an example of a full join in SQL:

TABLE A

order_id	column_a	column_b
1	data_a	data_b
2	data_c	data_d

TABLE B

order_id	column_c	column_d
1	data_e	data_f
3	data_g	data_h

SELECT *
FROM table_A
FULL JOIN table_B
ON table_A.order_id = table_B.order_id;

This query will return all rows from both tables, regardless of whether there's a matching arrange within the other table. This implies that even in case an order in Table A does not have any things in Table B, the row from Table A will still be included within the result set.

Benefits

The best thing about employing a full join in SQL is that it permits you to combine the results of two or more tables, even if there are no matches within the other table. This can be valuable after you are trying to get a total picture of the information.

Limitations

The main confinement of employing a full join in SQL is that it can be moderate and resource intensive, particularly when the tables being joined are huge. Furthermore, since it returns all rows from both tables, it can be troublesome to interpret the results.

Alternatives for Full Join

A union operation is the main alternative to a full join in SQL. A union operation combines the comes about of two or more tables, but it, as it were, returns distinct rows. This implies that in case an order has numerous things related with it, the query will, as it were, return the order once.

Common Mistakes of Full Join

One of the most common mistakes when using a full join in SQL is to forget to include the ON clause. The ON clause specifies the column or columns that should be used to join the two tables. Without the ON clause, the query will return all rows from both tables regardless of whether there is a match.

Key Takeaways for Full Join in SQL

Full Join in SQL is a type of join operation that combines the results of two or more tables.
It returns all rows when there's at slightest one match in either the left or right table.
The best thing about employing a full join in SQL is that it allows you to combine the results of two or more tables, even in the event that there are no matches within the other table.
The main limitation of employing a full join in SQL is that it can be slow and resource intensive.
The main alternative to a full join in SQL may be a union operation.
One of the foremost common mistakes when employing a full connect in SQL is to disregard to incorporate of the ON clause.

Conclusion

Akash successfully completed the task he was given. He utilized a full join in SQL to combine the information from two diverse tables, and he was able to urge the point-by-point report he required. His supervisors lauded his work, and they were exceptionally satisfied with the comes about.

Quiz

What type of join operation is a full join?
1. Inner Join
2. Left Join
3. Right Join
4. Outer Join

Answer: D. Outer Join

What does a full join in SQL return?
1. All rows from the left table
2. All rows from the right table
3. All rows from both tables
4. All rows from either table

Answer: C. All rows from both tables

What is a common mistake when using a full join in SQL?
1. Forgetting to include the WHERE clause
2. Forgetting to include the ORDER BY clause
3. Forgetting to include the ON clause
4. Forgetting to include the GROUP BY clause

Answer: C. Forgetting to include the ON clause

What is the main alternative to a full join in SQL?
1. Inner Join
2. Left Join
3. Right Join
4. Union

Answer: D. Union

Module 8: JOINS in SQL