在 MySQL 中使用 GROUP BY 获取行?
mysqlmysqli database更新于 2025/8/10 13:32:17
首先我们创建一个表 −
mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Subject varchar(20), Price int ); Query OK, 0 rows affected (0.64 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(Subject,Price) values('MySQL',456);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable(Subject,Price) values('MySQL',456);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable(Subject,Price) values('MongoDB',56);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable(Subject,Price) values('MongoDB',60);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable(Subject,Price) values('Java',100);
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable(Subject,Price) values('Java',130);
Query OK, 1 row affected (0.15 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable;
输出
+----+---------+-------+ | Id | Subject | Price | +----+---------+-------+ | 1 | MySQL | 456 | | 2 | MySQL | 456 | | 3 | MongoDB | 56 | | 4 | MongoDB | 60 | | 5 | Java | 100 | | 6 | Java | 130 | +----+---------+-------+ 6 rows in set (0.00 sec)
这是在 MySQL 中使用 GROUP BY 获取行的查询 −
mysql> select sum(Price) AS Total, Subject from DemoTable group by Subject;
输出
+-------+---------+ | Total | Subject | +-------+---------+ | 912 | MySQL | | 116 | MongoDB | | 230 | Java | +-------+---------+ 3 rows in set (0.04 sec)
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