SQL整理——语句
Having子句在 SQL 中增加 HAVING 子句原因是，WHERE 关键字无法与聚合函数一起使用，HAVING 子句可以让我们筛选分组后的各组数据。
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name
HAVING aggregate_function(column_name) operator value;
例：
A表Websites
idnameurlalexacountry1Googlehttps://www.google.cm1USA2淘宝https://www.taobao.com13CN3菜鸟教程http://www.runoob.com4689CN4微博http://weibo.com20CN5FaceBookhttps://www.facebook.com3USA B表access_log
idsite_idcountdate11452016-05-10231002016-05-13312302016-05-1442102016-05-14552052016-05-1464132016-05-15732202016-05-15855452016-05-16932012016-05-17 查找总访问量sum(count)>200,alexa排名小于30的网站。
select Websites.name,sum(access_log.count) AS TotalVisits
from Websites
INNER JOIN access_log
ON Websites.id = access_log.site_id
where Websites.alexa 200
页:
[1]