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;

Assume the two tables Customers and Orders are given as follows:

Customers
CustomerID	CustomerName
1	Raj
2	Neha
3	John
4	Anuj

Orders
OrderID	CustomerID	OrderAmount
101	1	4500
102	2	1200
103	1	2200
104	3	800

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 c.CustomerName, o.OrderAmount
   FROM Customers c INNER JOIN Orders o
   ON c.CustomerID = o.CustomerID;

⇒

CustomerName	OrderAmount
Raj	4500
Raj	2200
Neha	1200
John	800

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