如何在MySQL GROUP BY子句中排序或选择行？

让我们首先创建一个表-

mysql> create table DemoTable1572
   -> (
   -> StudentId int,
   -> StudentMarks int,
   -> StudentName varchar(20)
   -> );

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable1572 values(1,79,'Sam');
mysql> insert into DemoTable1572 values(2,89,'Chris');
mysql> insert into DemoTable1572 values(3,98,'David');
mysql> insert into DemoTable1572 values(4,79,'Bob');

使用select语句显示表中的所有记录-

mysql> select * from DemoTable1572;

这将产生以下输出-

+-----------+--------------+-------------+
| StudentId | StudentMarks | StudentName |
+-----------+--------------+-------------+
|         1 |           79 |       Sam   |
|         2 |           89 |       Chris |
|         3 |           98 |       David |
|         4 |           79 |       Bob   |
+-----------+--------------+-------------+
4 rows in set (0.00 sec)

这是对MySQL GROUP BY子句中的行进行排序或选择的查询-

mysql> select * from DemoTable1572
   -> where StudentId in (select min(StudentId) from DemoTable1572 group by StudentMarks);

这将产生以下输出-

+-----------+--------------+-------------+
| StudentId | StudentMarks | StudentName |
+-----------+--------------+-------------+
|         1 |           79 |       Sam   |
|         2 |           89 |       Chris |
|         3 |           98 |       David |
+-----------+--------------+-------------+
3 rows in set (0.10 sec)