INNER JOIN

INNER JOIN returns rows that have matching values in both tables. Unmatched rows are left out.

Example

sql

### SELECT Orders.OrderID, Customers.CustomerName

### FROM Orders

### INNER JOIN Customers

### ON Orders.CustomerID = Customers.CustomerID;

Result logic

For each order, find the customer with the same CustomerID:

Customers with no orders do not appear. Orders with no matching customer do not appear either.

Use table prefixes

Write Orders.OrderID instead of just OrderID to be clear which table a column comes from. This matters when both tables have a column with the same name (like CustomerID).

JOIN is shorthand for INNER JOIN

sql

### SELECT * FROM Orders
JOIN Customers ON Orders.CustomerID = Customers.CustomerID;

JOIN alone means INNER JOIN.

TL;DR

• INNER JOIN returns only matching rows.
• The ON clause defines the match.
• Use table prefixes to avoid ambiguity.
• JOIN alone means INNER JOIN.