LEFT JOIN Practice

LEFT JOIN returns ALL rows from the left table, plus matching rows from the right table. If there's no match, you get NULL values for the right table's columns.

LEFT JOIN Visualization

Table A (LEFT)    Table B
+----+            +----+
| 1  |    JOIN    | 1  |  ← Matched
| 2  |    ====    | 3  |
| 3  |            | 4  |
+----+            +----+

Result:
| A | B    |
|---|------|
| 1 | 1    |  ← Matched
| 2 | NULL |  ← No match, but included with NULL
| 3 | 3    |  ← Matched

When to Use LEFT JOIN

Use LEFT JOIN when you want ALL records from one table, regardless of whether they have related records in another table.

Example: "Show all users, including those who haven't placed orders"

Exercises

INNER vs LEFT JOIN

JOIN Type	Returns
INNER JOIN	Only matching rows from both tables
LEFT JOIN	All rows from left table + matches from right

Free Practice

Try:

• Find categories with no products
• List all products with order counts (including 0)
• Compare LEFT JOIN vs INNER JOIN results