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Introduction to MySQL Outer Join

MySQL Outer Join is considered to be three types: –

• FULL OUTER Join
• LEFT OUTER Join – same as left join.
• RIGHT OUTER Join – same as right join.

FULL OUTER JOIN

Full Join gets all the rows from both tables. In this section, let’s discuss more FULL join which is used mostly.

Example:

Below represents the Venn diagram of the FULL join.

Syntax:

SELECT * FROM TABLE_A A
FULL OUTER JOIN TABLE_B B
ON A. Common_COLUMN =B. Common_COLUMN
WHERE

The result set contains NULL set values. Below syntax can be used to neglect the NULL values: –

SELECT * FROM TABLE_A A
FULL OUTER JOIN TABLE B B
ON A. Common_COLUMN =B. Common_COLUMN
WHERE A.Common_COLUMN IS NULL
AND A.Common_COLUMN IS NULL

Key Differences of Full Outer Join vs Right Join

Let us discuss the main differences of Full Outer Join and Right Join.

How to use FULL Outer Join in MySQL?

• FULL Outer Join = All rows from both tables
• Consider all rows from both tables. Unmatched rows get null values
• Joins based on a condition
• ON keyword is used to specify the condition and join the tables.

Examples

Here are the following examples mention below

Example #1

Let us consider two tables and apply FULL outer join on the tables:

Loan Table:

Borrower Table:

Query to get the loan_no, status, and borrower date from two tables.

Query:

SELECT L.LOAN_NO, L.LOAN_STATUS, B.BORROWER_DATE
FROM LOAN L FULL OUTER JOIN BORROWER B
ON L.LOAN_NO=B.LOAN_NO

Let’s check the output of the above table after applying the right join on them.

Output:

The result set contains NULL set values.

Below syntax can be used to neglect the NULL values: –

SELECT * FROM TABLE_A A
FULL OUTER JOIN TABLE B B
ON A. Common_COLUMN =B. Common_COLUMN
WHERE A.Common_COLUMN IS NULL

Let us consider two tables and apply FULL Outer join on the tables:

Query to get the loan_no, status, loan_aount and borrower date from two tables.

Query:

SELECT L.LOAN_NO, L.LOAN_STATUS,L.LOAN_AMOUNT, B.BORROWER_DATE
FROM LOAN L FULL OUTER JOIN BORROWER B
ON L.LOAN_NO=B.LOAN_NO

Let’s check the output of the above table after applying the Full outer join on them.

Output:

In the above table, LOAN is the right table and the Borrower is the left table. As in FULL OUTER join, we get all rows from both tables. Here we get all the rows from the LOAN table and the Borrower table. Values not present will be NULL.

Example #2

Let us consider two tables and apply FULL OUTER join on the tables:

Query to get the loan_no, status, loan_aount and borrower date from two tables.

Query:

SELECT L.LOAN_NO, L.LOAN_STATUS,L.LOAN_AMOUNT, B.BANK_ID
FROM BORROWER B FULL OUTER JOIN LOAN L
ON L.LOAN_NO=B.LOAN_NO

Let’s check the output of the above table after applying the FULL OUTER join on them.

Output:

In the above table, LOAN is the right table and the Borrower is the left table. As in FULL OUTER join, we get all rows from both tables. Here we get all the rows from the LOAN table and the Borrower table. Values not present will be NULL.

Conclusion

To fetch data relevant to the customer requirement we might need to join tables which will be fulfilled by joins. As mentioned earlier joins are used to get data from more than one table. To join more than one table we need at least one column common in both tables. Tables get joined based on the condition specified.

Recommended Articles

This is a guide to MySQL Outer Join. Here we discuss how to use FULL Outer Join in MySQL along with the key differences between full outer join vs right join and examples. You may also have a look at the following articles to learn more –

1. Table in MySQL
2. MySQL Aggregate Function
3. LEFT OUTER JOIN in PostgreSQL | Examples
4. LEFT OUTER JOIN in SQL | How to Works?