https://yrunz.com/tags/sql/ Recent content in SQL on 元闰子的邀请 Hugo -- gohugo.io en-us Sun, 03 Jul 2022 00:00:00 +0000 https://yrunz.com/p/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3-sql-%E4%B8%AD%E7%9A%84-grouping-sets-%E8%AF%AD%E5%8F%A5/ Sun, 03 Jul 2022 00:00:00 +0000 https://yrunz.com/p/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3-sql-%E4%B8%AD%E7%9A%84-grouping-sets-%E8%AF%AD%E5%8F%A5/ 前言 SQL 中 Group By 语句大家都很熟悉，根据指定的规则对数据进行分组，常常和聚合函数一起使用。 比如，考虑有表 dealer，表中数据如下： id (Int) city (String) car_model (String) quantity (Int) 100 Fremont Honda Civic 10 100 Fremont Honda Accord 15 100 Fremont Honda CRV 7 200 Dublin Honda Civic 20 200 Dublin Honda Accord 10 200 Dublin Honda CRV 3 300 San Jose Honda Civic 5 300 San Jose Honda Accord 8 如果执行 SQL 语句 SELECT id, sum(quantity) FROM dealer GROUP BY id ORDER BY id，会得到如下结果：