查找不同学科学生的平均成绩并仅显示MySQL中最高的平均成绩
为此，您可以使用子查询。让我们首先创建一个表-
mysql> create table DemoTable ( StudentName varchar(40), StudentMarks int );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values('Adam',56);
mysql> insert into DemoTable values('Chris',78);
mysql> insert into DemoTable values('Adam',89);
mysql> insert into DemoTable values('Robert',98);
mysql> insert into DemoTable values('Chris',65);
mysql> insert into DemoTable values('Robert',34);使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
这将产生以下输出-
+-------------+--------------+ | StudentName | StudentMarks | +-------------+--------------+ | Adam | 56 | | Chris | 78 | | Adam | 89 | | Robert | 98 | | Chris | 65 | | Robert | 34 | +-------------+--------------+ 6 rows in set (0.00 sec)
以下是查找学生的平均成绩并仅显示最高平均成绩的查询-
mysql> select max(avSal.StudentMarks) from (select avg(StudentMarks) as `StudentMarks` from DemoTable group by StudentName) as avSal;
这将产生以下输出-
+-------------------------+ | max(avSal.StudentMarks) | +-------------------------+ | 72.5000 | +-------------------------+ 1 row in set (0.09 sec)