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SQL INNER JOIN keywords

SQL INNER JOIN keywords

INNER JOIN keyword return rows when the presence of at least one match in the table.

SQL INNER JOIN syntax

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

or:

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

Note: INNER JOIN and JOIN is the same.

SQL INNER JOIN

The demo database

In this tutorial, we will use w3big sample database.

The following is a selected "Websites" table data: 

+----+--------------+---------------------------+-------+---------+
| id | name         | url                       | alexa | country |
+----+--------------+---------------------------+-------+---------+
| 1  | Google       | https://www.google.cm/    | 1     | USA     |
| 2  | 淘宝          | https://www.taobao.com/   | 13    | CN      |
| 3  | 本教程      | http://www.w3big.com/    | 4689  | CN      |
| 4  | 微博          | http://weibo.com/         | 20    | CN      |
| 5  | Facebook     | https://www.facebook.com/ | 3     | USA     |
| 7  | stackoverflow | http://stackoverflow.com/ |   0 | IND     |
+----+---------------+---------------------------+-------+---------+

Here is the data "access_log" website access record table: 

mysql> SELECT * FROM access_log;
+-----+---------+-------+------------+
| aid | site_id | count | date       |
+-----+---------+-------+------------+
|   1 |       1 |    45 | 2016-05-10 |
|   2 |       3 |   100 | 2016-05-13 |
|   3 |       1 |   230 | 2016-05-14 |
|   4 |       2 |    10 | 2016-05-14 |
|   5 |       5 |   205 | 2016-05-14 |
|   6 |       4 |    13 | 2016-05-15 |
|   7 |       3 |   220 | 2016-05-15 |
|   8 |       5 |   545 | 2016-05-16 |
|   9 |       3 |   201 | 2016-05-17 |
+-----+---------+-------+------------+
9 rows in set (0.00 sec)

Examples of SQL INNER JOIN

The following SQL statement will return all records access websites:

Examples

SELECT Websites.name, access_log.count, access_log.date
FROM Websites
INNER JOIN access_log
ON Websites.id = access_log.site_id
ORDER BY access_log.count;

Execute the above SQL output results are as follows:

Note: INNER JOIN keyword return rows when the presence of at least one match in the table. If the "Websites" table row "access_log" does not match, these lines will not be listed.