ORDER BY rand()并将其分组在MySQL中？

让我们首先创建一个表-

mysql> create table DemoTable
   -> (
   -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   -> StudentMarks int
   -> );

使用insert命令在表中插入一些记录。我们还插入了重复记录-

mysql> insert into DemoTable(StudentMarks) values(98);
mysql> insert into DemoTable(StudentMarks) values(98);
mysql> insert into DemoTable(StudentMarks) values(78);
mysql> insert into DemoTable(StudentMarks) values(78);
mysql> insert into DemoTable(StudentMarks) values(45);
mysql> insert into DemoTable(StudentMarks) values(56);

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-

+-----------+--------------+
| StudentId | StudentMarks |
+-----------+--------------+
| 1         | 98           |
| 2         | 98           |
| 3         | 78           |
| 4         | 78           |
| 5         | 45           |
| 6         | 56           |
+-----------+--------------+
6 rows in set (0.00 sec)

以下是通过rand()将它们分组来排序的查询-

mysql> select *from DemoTable order by rand(StudentMarks*100*RAND());

这将产生以下输出。在这里，标记98记录保持分组-

+-----------+--------------+
| StudentId | StudentMarks |
+-----------+--------------+
| 3         | 78           |
| 6         | 56           |
| 5         | 45           |
| 4         | 78           |
| 1         | 98           |
| 2         | 98           |
+-----------+--------------+
6 rows in set (0.00 sec)