The INNER JOIN keyword return rows when there is at least one match in both tables.
SQL INNER JOIN Syntax
SELECT column_name(s) FROM table_name1 INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name
PS: INNER JOIN is the same as JOIN.
SQL INNER JOIN Example
The “Persons” table:
| P_Id | LastName | FirstName | Address | City |
|---|---|---|---|---|
| 1 | Hansen | Ola | Timoteivn 10 | Sandnes |
| 2 | Svendson | Tove | Borgvn 23 | Sandnes |
| 3 | Pettersen | Kari | Storgt 20 | Stavanger |
The “Orders” table:
| O_Id | OrderNo | P_Id |
|---|---|---|
| 1 | 77895 | 3 |
| 2 | 44678 | 3 |
| 3 | 22456 | 1 |
| 4 | 24562 | 1 |
| 5 | 34764 | 15 |
Now we want to list all the persons with any orders. We use the following SELECT statement:
SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons INNER JOIN Orders ON Persons.P_Id=Orders.P_Id ORDER BY Persons.LastName
The result-set will look like this:
| LastName | FirstName | OrderNo |
|---|---|---|
| Hansen | Ola | 22456 |
| Hansen | Ola | 24562 |
| Pettersen | Kari | 77895 |
| Pettersen | Kari | 44678 |
The INNER JOIN keyword return rows when there is at least one match in both tables. If there are rows in “Persons” that do not have matches in “Orders”, those rows will NOT be listed.
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