SQL INNER JOIN

SQL INNER JOIN 關(guān)鍵字

INNER JOIN 關(guān)鍵字在表中存在至少一個匹配時返回行。

SQL INNER JOIN 語法

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;

注釋：INNER JOIN 與 JOIN 是相同的。

SQL INNER JOIN

演示數(shù)據(jù)庫

在本教程中，我們將使用 JSON 樣本數(shù)據(jù)庫。

下面是選自 "Websites" 表的數(shù)據(jù)：

+----+--------------+---------------------------+-------+---------+
| id | name         | url                       | alexa | country |
+----+--------------+---------------------------+-------+---------+
| 1  | Google       | https://www.google.cm/    | 1     | USA     |
| 2  | 淘寶          | https://www.taobao.com/   | 13    | CN      |
| 3  | 小白教程      | http://9t9t.com.cn    | 888  | 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" 網(wǎng)站訪問記錄表的數(shù)據(jù)：

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 實(shí)例

下面的 SQL 語句將返回所有網(wǎng)站的訪問記錄：

實(shí)例

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;

注釋：INNER JOIN 關(guān)鍵字在表中存在至少一個匹配時返回行。如果 "Websites" 表中的行在 "access_log" 中沒有匹配，則不會列出這些行。

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