SQL LEFT JOIN Keyword

The LEFT JOIN keyword returns all records from the left table (table1), and the matched records from the right table (table2). The result is NULL from the right side if there is no match.

Syntax

SELECT columns
FROM table1
LEFT JOIN table2
ON table1.common_column = table2.common_column;

Example: LEFT JOIN

SELECT employees.name, departments.department_name
FROM employees
LEFT JOIN departments
ON employees.department_id = departments.id;

Sample Tables

Consider the following two tables:

Employees Table

| id | name        | department_id |
|----|-------------|---------------|
| 1  | John Doe    | 1             |
| 2  | Jane Smith  | 2             |
| 3  | Mike Johnson| 1             |
| 4  | Emily Davis | 3             |
| 5  | Sarah Connor| 4             |

Departments Table

| id | department_name |
|----|-----------------|
| 1  | HR              |
| 2  | Sales           |
| 3  | IT              |

Result of LEFT JOIN

| name        | department_name |
|-------------|-----------------|
| John Doe    | HR              |
| Jane Smith  | Sales           |
| Mike Johnson| HR              |
| Emily Davis | IT              |
| Sarah Connor| NULL            |

All employees are returned. Sarah Connor has no matching department, so department_name is NULL.