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SQL INNER JOIN 关键字

减小字体 增大字体 作者:佚名  来源:网上搜集  发布时间:2019-1-11 14:11:34

SQL INNER JOIN 关键字SQL 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。SQL INNER JOIN 语法SELECT column_name(s)FROM table1INNER JOIN table2ON table1.column_name=table2.column_name;或:SELECT column_name(s)FROM table1JOIN table2ON table1.column_name=table2.column_name;注释:INNER JOIN 与 JOIN 是相同的。演示数据库在本教程中,我们将使用 RUNOOB 样本数据库。下面是选自 "Websites" 表的数据:+----+--------------+---------------------------+-------+---------+| id | name | url | alexa | country |+----+--------------+---------------------------+-------+---------+| 1 | Google | https:





//www.google.cm/ | 1 | USA || 2 | 淘宝 | https:





//www.taobao.com/ | 13 | CN || 3 | k88.net | http:





//www.k88.net/ | 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 |+-----+---------+-------+------------+9 rows in set (0.00 sec)SQL INNER JOIN 实例下面的 SQL 语句将返回所有网站的访问记录:实例SELECT Websites.name, access_log.count, access_log.dateFROM WebsitesINNERJOIN access_logON Websites.id=access_log.site_idORDER BYaccess_log.count;执行以上 SQL 输出结果如下: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。

SQL INNER JOIN 关键字