An INNER JOIN is a term used in SQL (Structured Query Language) to combine rows from two (or more) tables based on a related column between them.
You have two tables:
Table: Customers
| CustomerID | Name |
|---|---|
| 1 | Anna |
| 2 | Bernd |
| 3 | Clara |
Table: Orders
| OrderID | CustomerID | Product |
|---|---|---|
| 101 | 1 | Book |
| 102 | 2 | Laptop |
| 103 | 4 | Phone |
Now you want to know which customers have placed orders. You only want the customers who exist in both tables.
SELECT Customers.Name, Orders.Product
FROM Customers
INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID;| Name | Product |
|---|---|
| Anna | Book |
| Bernd | Laptop |
Clara didn’t place any orders → not included.
The order with CustomerID 4 doesn’t match any customer → also excluded.
An INNER JOIN returns only the rows with matching values in both tables.
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