INNER JOIN 关键字)

INNER JOIN 关键字

INNER JOIN 关键字在表中存在至少一个匹配时返回行。

语法

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

或：

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

注释 ： INNER JOIN 与 JOIN 是相同的。

示例

示例使用 样本数据库。

该库包含 "Websites" 表：

+----+--------------+---------------------------+-------+---------+
| id | name         | url                       | alexa | country |
+----+--------------+---------------------------+-------+---------+
| 1  | Google       | https://www.google.cm/    | 1     | USA     |
| 2  | 淘宝          | https://www.taobao.com/   | 13    | CN      |
| 3  | 菜鸟教程      | http://www.runoob.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     |
+----+---------------+---------------------------+-------+---------+

下面是 "access_log" 网站访问记录表的数据：

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 |
+-----+---------+-------+------------+

INNER JOIN 示例

返回所有网站的访问记录：

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;

输出结果：

mysql> 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;

+---------+---------+------------+
| name    | count   | date       |
+---------+---------+------------+
| 淘宝     |  10     | 2016-05-14 |
| 微博    |   13     | 2016-05-15 |
| Google  |   45    | 2016-05-10 |
| 菜鸟教程 |   100   | 2016-05-13 |
| 菜鸟教程 |  201    | 2016-05-17 |
| Facebook|   205   | 2016-05-14 |
| 菜鸟教程 |  220    | 2016-05-15 |
| Google  |   230   | 2016-05-14 |
| Facebook|  545    | 2016-05-16 |
+---------+--------+-------------+

注释 ： INNER JOIN 关键字在表中存在至少一个匹配时返回行。如果 "Websites" 表中的行在 "access_log" 中没有匹配，则不会列出这些行。