MySQL 查询按字母顺序排列记录并计算重复项?
mysqlmysqli database更新于 2025/7/19 15:40:17
为此，请同时使用 GROUP BY 和 ORDER BY 子句。让我们首先创建一个表 −
mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentGrade char(1) ); Query OK, 0 rows affected (0.87 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(StudentGrade) values('A');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable(StudentGrade) values('F');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable(StudentGrade) values('C');
Query OK, 1 row affected (0.28 sec)
mysql> insert into DemoTable(StudentGrade) values('A');
Query OK, 1 row affected (0.23 sec)
mysql> insert into DemoTable(StudentGrade) values('F');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable(StudentGrade) values('F');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable(StudentGrade) values('B');
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable(StudentGrade) values('C');
Query OK, 1 row affected (0.13 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable;
输出
+-----------+--------------+ | StudentId | StudentGrade | +-----------+--------------+ | 1 | A | | 2 | F | | 3 | C | | 4 | A | | 5 | F | | 6 | F | | 7 | B | | 8 | C | +-----------+--------------+ 8 rows in set (0.00 sec)
这是按字母顺序排列并计数的查询 −
mysql> select StudentGrade,count(StudentId) as Frequency from DemoTable group by StudentGrade order by StudentGrade;
输出
+--------------+-----------+ | StudentGrade | Frequency | +--------------+-----------+ | A | 2 | | B | 1 | | C | 2 | | F | 3 | +--------------+-----------+ 4 rows in set (0.00 sec)
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