How to join three tables in SQL using JOINS

A basic SQL approach called joining tables allows you to join data from multiple tables based on a common column. The method is the same as joining two tables plus one extra step for joining three tables. In this article, you will learn How to join three tables using SQL joins.

How to join three tables in SQL using JOINS

Before moving to joining three tables first let's understand the types of JOINS in SQL

1. INNER JOIN: This returns records that have matching values in both tables.

2. LEFT JOIN (or LEFT OUTER JOIN): This JOIN method returns all the records from the left table and the matched records from the right table. Records from the left table that do not have a match in the right table will have NULL values in columns from the right table.

3. RIGHT JOIN (or RIGHT OUTER JOIN): This method will return all the records from the right table and the matched records from the left table. Records from the right table that do not have a match in the left table will have NULL values in columns from the left table.

4. FULL JOIN (or FULL OUTER JOIN): The FULL JOIN method will return all the records when there is a match in either the left or right table. Records that do not match in either table will have NULL values.


Now let's take an example of three tables in MYSQL and join all the three tables using JOINS method:

Table: students

id name father_name age
1 Ram Shyam 20
2 Mohan Ramphal 25

Table: courses

id course_name student_id fee
101 HTML 1 500
102 CSS 2 799

Table: class

id class timing student_id
1000 BCA 9-5 2
1001 BCA 12-9 1


Here is the query to JOIN all of these tables based on student_id

SELECT * FROM students as A JOIN courses as B on A.id = B.student_id JOIN class as C on B.student_id = C.student_id WHERE A.id = 1;


Output

id name father_name age id course_name student_id fee id class timing student_id
1 Ram Shyam 20 1 HTML 1 500 2 BCA 12-9 1

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