Slide 14.17: The (INNER) JOIN clause

Slide 14.16: Top SQL joins
Slide 14.18: The LEFT (OUTER) JOIN clause
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The (INNER) JOIN Clause

The (INNER) JOIN clause is used to combine rows from two or more tables, based on a related column between them.

 SELECT column_name(s)
  FROM table1 INNER JOIN table2
  ON table1.column_name = table2.column_name;

Let’s look at a selection from the Orders table:

OrderID	CustomerID	OrderDate
10308	2	2025-09-18
10309	37	2025-09-19
10310	77	2025-19-20

Then, look at the selection from the Customers table:

CustomerID	CustomerName	ContactName	Country
1	Alfreds Futterkiste	Maria Anders	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mexico

Notice that the CustomerID column in the Orders table refers to the CustomerID in the Customers table. The relationship between the two tables above is the CustomerID column. Then, we can create the following SQL statement (that contains an INNER JOIN), that selects records that have matching values in both tables:

 SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
   FROM Orders INNER JOIN Customers
   ON Orders.CustomerID=Customers.CustomerID;

and it will produce something like this:

OrderID	CustomerName	OrderDate
10308	Ana Trujillo Emparedados y helados	9/18/2025
10365	Antonio Moreno Taquería	11/27/2025
10383	Around the Horn	12/16/2025
10355	Around the Horn	11/15/2025
10278	Berglunds snabbköp	8/12/2025

Demonstration
Below is an SQL test area from W3Schools, which uses the well-known Northwind sample database. The tables here are for read only because of the problem of embedding the scripts. For a fully working example, check this by using Chrome.

Result:

The Database includes:

Tablename	Record
Customers	91
Categories	8
Employees	10
OrderDetails	518
Orders	196
Products	77
Shippers	3
Suppliers	29

W3C WebSQL

WebSQL Browser Support