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-- View the students table
SELECT * FROM students;

-- View the enrollments table
SELECT * FROM enrollments;

-- View all students and their classes, including those with no enrollment
SELECT students.name, enrollments.class_name
FROM students
LEFT JOIN enrollments
ON students.student_id = enrollments.student_id;

# LEFT JOIN

A `LEFT JOIN` returns **all rows from the left table** along with any matching rows from the right table.

If there is no match, the result shows `NULL` for columns from the right table.

<br/>

## Syntax

Here is the syntax for a `LEFT JOIN`:

```sql title="LEFT JOIN Syntax"
SELECT columns
FROM table1
LEFT JOIN table2
ON table1.column = table2.column;
```

* The *left table* (`table1`) is listed first.
* All rows from the left table are included, even if there is *no match* in the right table.

<br/>

## Example: Students and Enrollments

Below is an example of a `LEFT JOIN` between the `students` and `enrollments` tables.

*students*

| student_id | name          |
| ----------- | ------------- |
| 1           | John Miller   |
| 2           | Lisa Brown    |
| 3           | David Smith   |
| 4           | Emily Davis   |
| 5           | Michael Jones |

*enrollments*

| student_id | class_name |
| ----------- | ----------- |
| 1           | Math        |
| 1           | Science     |
| 2           | History     |
| 5           | Art         |

```sql title="LEFT JOIN example"
SELECT students.name, enrollments.class_name
FROM students
LEFT JOIN enrollments
ON students.student_id = enrollments.student_id;
```

### Result:

| name          | class_name |
| ------------- | ----------- |
| John Miller   | Math        |
| John Miller   | Science     |
| Lisa Brown    | History     |
| David Smith   | NULL        |
| Emily Davis   | NULL        |
| Michael Jones | Art         |

> David Smith and Emily Davis included even though they have no enrollments.

<br/>

## How is `LEFT JOIN` useful?

Use `LEFT JOIN` when you want to:  
- Keep all rows from the left table, regardless of matches  
- Identify records in the left table without corresponding entries in the right table  
- Build full lists, such as all customers with or without purchases

In a LEFT JOIN, all rows from the left table are included in the result, with matching rows from the right table. If there is no match, the result will have NULL for columns from the right table, not the other way around.

### In a LEFT JOIN operation, unmatched rows from the right table will be included with NULL values for their columns in the result.

student_id	name
1	John Miller
2	Lisa Brown
3	David Smith
4	Emily Davis
5	Michael Jones

name	class_name
John Miller	Math
John Miller	Science
Lisa Brown	History
David Smith	NULL
Emily Davis	NULL
Michael Jones	Art

LEFT JOIN

Syntax

Example: Students and Enrollments

Result:

How is LEFT JOIN useful?

In a LEFT JOIN operation, unmatched rows from the right table will be included with NULL values for their columns in the result.

How is `LEFT JOIN` useful?