Part 62: INNER JOIN: Matching Rows Across Multiple Tables

The most commonly used join. An INNER JOIN returns only the records that have matching values in both tables.

1. Syntax

SELECT 
  orders.id AS order_id,
  users.first_name,
  users.last_name,
  orders.total_amount
FROM orders
INNER JOIN users ON orders.user_id = users.id;

2. Table Aliases for Readability

Always use short, descriptive table aliases to keep complex joins readable:

SELECT 
  o.id,
  u.email,
  o.total_amount
FROM orders o
JOIN users u ON o.user_id = u.id;

(Note: JOIN without specifying INNER defaults to INNER JOIN).

Key Takeaways

• INNER JOIN discards any rows that fail the ON condition in either table.

In Part 63, we will explore LEFT (OUTER) JOIN: Preserving Unmatched Left Rows!