JOINS

MySQL JOINS are used with SELECT statement. It is used to retrieve data from multiple tables. It is performed whenever you need to fetch records from two or more tables.

There are three types of MySQL joins:

• MySQL INNER JOIN (or sometimes called simple join)
• MySQL LEFT OUTER JOIN (or sometimes called LEFT JOIN)
• MySQL RIGHT OUTER JOIN (or sometimes called RIGHT JOIN)

MySQL Inner JOIN (Simple Join)

The MySQL INNER JOIN is used to return all rows from multiple tables where the join condition is satisfied. It is the most common type of join.

Syntax:

SELECT columns  

FROM table1   

INNER JOIN table2  

ON table1.column = table2.column;

Image representation:

Let’s take an example:

Consider two tables “officers” and “students”, having the following data.

Execute the following query:

SELECT officers.officer_name, officers.address, students.course_name  

FROM officers   

INNER JOIN students  

ON officers.officer_id = students.student_id;  

Output:

MySQL Left Outer Join

The LEFT OUTER JOIN returns all rows from the left hand table specified in the ON condition and only those rows from the other table where the join condition is fulfilled.

Syntax:

  SELECT columns  

FROM table1  

LEFT [OUTER] JOIN table2  

ON table1.column = table2.column;  

Image representation:

Let’s take an example:

Consider two tables “officers” and “students”, having the following data.

Execute the following query:

 SELECT  officers.officer_name, officers.address, students.course_name  

FROM officers  

LEFT JOIN students  

ON officers.officer_id = students.student_id; 

Output:

MySQL Right Outer Join

The MySQL Right Outer Join returns all rows from the RIGHT-hand table specified in the ON condition and only those rows from the other table where he join condition is fulfilled.

Syntax:

 SELECT columns  

FROM table1  

RIGHT [OUTER] JOIN table2  

ON table1.column = table2.column; 

Image representation:

Let’s take an example:

Consider two tables “officers” and “students”, having the following data.

Execute the following query:

 SELECT officers.officer_name, officers.address, students.course_name, students.student_name  

FROM officers  

RIGHT JOIN students  

ON officers.officer_id = students.student_id; 

Output: