MySQL LEFT JOIN: Definition, Syntax, and Examples

A LEFT JOIN in MySQL is used to retrieve all records from the left table (first table) and the matching records from the right table (second table).

If there is no match found in the right table, NULL values are returned for the right table's columns.
It is also known as a Left Outer Join.

LEFT JOIN Syntax

SELECT table1.column_name, table2.column_name
FROM table1
LEFT JOIN table2
ON table1.common_column = table2.common_column;

table1 → Left table
table2 → Right table
ON → Specifies the relationship between columns in both tables

Example Scenario:

Students Table:

student_id	name	gender	city	age	score	course_id	email	phone_number
1	Alice	Female	Delhi	20	85	101	NULL	1234567890
2	Bob	Male	Mumbai	22	75	NULL	bob@email.com	NULL
3	Charlie	Male	Delhi	21	95	102	NULL	NULL
4	David	Male	Bangalore	23	65	101	david@email.com	NULL
5	Eve	Female	Mumbai	20	80	103	NULL	NULL
6	Frank	Male	Delhi	22	90	103	NULL	NULL
7	Alice	Female	Mumbai	19	60	102	NULL	NULL

Courses Table:

course_name	course_name
101	Math
102	Science
103	History
104	English

The following SQL statement will select all students, and any courses they might have:

Example

SELECT courses.course_name,students.name

FROM courses

LEFT JOIN students

ON students.course_id = courses.course_id;

Try it yourself

Output:

name	course_name
Alice	Math
Bob	NULL
Charlie	Science
David	Math
Eve	History
Frank	History
Alice	Science

Explanation:

Alice is matched with the Math course.
Charlie is matched with the Science course.
Bob has no course (NULL in course_id), so the result shows NULL in course_name.

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