SQL有
SQL HAVING子句
HAVING 子句
在SQL 中增加HAVING 子句原因是，WHERE 關鍵字無法與聚合函數一起使用。
HAVING 子句可以讓我們篩選分組後的各組資料。
SQL HAVING 語法
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value # ) operator value;
FROM table_name
WHERE column_name operator value # ) operator value;
示範資料庫
#在本教學中，我們將使用php 樣本資料庫。
下面是選自"Websites" 表的資料：
+----+--------------+--- ------------------------+-------+---------+| id | name | url | alexa | country |
+----+----------+------------------------------------ --------+-------+---------+
| 1 | Google | https://www.google.cm/ | 1 | USA | 1 |
| 2 | 淘寶 | https://www.taobao.com/ | 13 | CN cn/ | 4689 | CN |
| 4 | 微博 | http://weibo.com/ | 201 https://www.facebook.com/ | 3 | USA |
| 7 | stackoverflow | http://stackoverflow.com/ | 0 | IND |
+----+---------------+----------- ------------------+-------+---------+
#
SQL HAVING 實例現在我們想要找出總訪問量大於200 的網站。 我們使用下面的 SQL 語句：
#| 1 | Google | https://www.google.cm/ | 1 | USA | 1 |
| 2 | 淘寶 | https://www.taobao.com/ | 13 | CN cn/ | 4689 | CN |
| 4 | 微博 | http://weibo.com/ | 201 https://www.facebook.com/ | 3 | USA |
| 7 | stackoverflow | http://stackoverflow.com/ | 0 | IND |
+----+---------------+----------- ------------------+-------+---------+
#
以下是"access_log" 網站存取記錄表的資料：
mysql> SELECT * FROM access_log;
+-----+--------- +-------+------------+
| aid | site_id | count | date |
+-----+------ ---+-------+------------+
| 1 | 1 | 45 | 2016-05-10 |#1 | 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 |
| -15 |
| 8 | 5 | 545 | 2016-05 -16 |
| 9 | 3 | 201 | 2016-05-17 |
+-----+---------+-------+----- ---------+
9 rows in set (0.00 sec)
+-----+--------- +-------+------------+
| aid | site_id | count | date |
+-----+------ ---+-------+------------+
| 1 | 1 | 45 | 2016-05-10 |#1 | 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 |
| -15 |
| 8 | 5 | 545 | 2016-05 -16 |
| 9 | 3 | 201 | 2016-05-17 |
+-----+---------+-------+----- ---------+
9 rows in set (0.00 sec)
SQL HAVING 實例現在我們想要找出總訪問量大於200 的網站。 我們使用下面的 SQL 語句：
實例SELECT Websites.name, Websites.url, SUM(access_log.count) AS nums FROM
(access_log
##現在我們想要找出總訪問量大於200 的網站，且alexa 排名小於200。
INNER JOIN Websites
ON access_log.site_id=Websites.id)
GROUP BY Websites.name
HAVING SUM(access_log.count) > 200;
執行上述SQL 輸出結果如下：ON access_log.site_id=Websites.id)
GROUP BY Websites.name
HAVING SUM(access_log.count) > 200;
我們在 SQL 語句中增加一個普通的 WHERE 子句：
實例SELECT Websites.name, SUM(access_log.count) AS nums FROM Websites
INNER JOIN access_logON Websites.id=access_log.site_id
WHERE Websites.alexa < 200
GROUP BY Websites.name
HAVING SUM(access_log.count) > 200;
WHERE Websites.alexa < 200
GROUP BY Websites.name
HAVING SUM(access_log.count) > 200;
執行上述 SQL 輸出結果如下：
