MySQL查询以字母顺序记录和计数重复项？
为此，请同时使用GROUPBY和ORDERBY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) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable(StudentGrade) values('A');
mysql> insert into DemoTable(StudentGrade) values('F');
mysql> insert into DemoTable(StudentGrade) values('C');
mysql> insert into DemoTable(StudentGrade) values('A');
mysql> insert into DemoTable(StudentGrade) values('F');
mysql> insert into DemoTable(StudentGrade) values('F');
mysql> insert into DemoTable(StudentGrade) values('B');
mysql> insert into DemoTable(StudentGrade) values('C');使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
输出结果
+-----------+--------------+ | 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和计数的查询-
mysql> select StudentGrade,count(StudentId) as Frequency from DemoTable group by StudentGrade order by StudentGrade;
输出结果
+--------------+-----------+ | StudentGrade | Frequency | +--------------+-----------+ | A | 2 | | B | 1 | | C | 2 | | F | 3 | +--------------+-----------+ 4 rows in set (0.00 sec)