SQL INNER JOIN Explained

What is an INNER JOIN?

An INNER JOIN combines rows from two tables based on a related column between them. It returns only the rows where the join condition is true.

If there is no match between the tables, those rows are excluded from the result.

• Matches rows based on a specified condition.
• Returns only rows with matching values in both tables.
• Excludes rows without a match.

INNER JOIN Syntax

The basic syntax for an INNER JOIN is:

You specify the tables to join and the condition that relates them.

• SELECT columns FROM table1
• INNER JOIN table2 ON table1.column = table2.column;

Example of INNER JOIN

Consider two tables: Customers and Orders. To find all customers who have placed orders, you can use INNER JOIN on the CustomerID column.

How INNER JOIN Works

The INNER JOIN compares each row of the first table with each row of the second table to find all pairs of rows that satisfy the join condition.

Only those pairs are included in the result set.

• Evaluates join condition for each row pair.
• Includes rows where condition is true.
• Excludes rows without matching pairs.

When to Use INNER JOIN

Use INNER JOIN when you want to retrieve records that have matching values in both tables.

It is ideal for combining related data where both sides must have corresponding entries.

• To find matching records across tables.
• When you want to exclude unmatched rows.
• For filtering data based on relationships.