无涯教程-SQL RAND Function函数

SQL具有 RAND 函数，可以调用该函数以生成介于0和1之间的随机数-

SQL>  SELECT RAND( ), RAND( ), RAND( );
+------------------+-----------------+------------------+
| RAND( )          | RAND( )         | RAND( )          |
+------------------+-----------------+------------------+
| 0.45464584925645 | 0.1824410643265 | 0.54826780459682 |
+------------------+-----------------+------------------+
1 row in set (0.00 sec)

当使用整数参数调用时，RAND()使用该值作为随机数生成器的种子。每次使用给定值为生成器播种时，RAND()将产生可重复的数字序列-

SQL>  SELECT RAND(1), RAND( ), RAND( );
+------------------+------------------+------------------+
| RAND(1 )         | RAND( )          | RAND( )          |
+------------------+------------------+------------------+
| 0.18109050223705 | 0.75023211143001 | 0.20788908117254 |
+------------------+------------------+------------------+
1 row in set (0.00 sec)

您可以使用 ORDER BY RAND()将一组行或值随机化，如下所示-

要了解 ORDER BY RAND()函数，请考虑 employee_tbl 表，该表具有以下记录-

SQL> SELECT * FROM employee_tbl;
+------+------+------------+--------------------+
| id   | name | work_date  | daily_typing_pages |
+------+------+------------+--------------------+
|    1 | John | 2007-01-24 |                250 |
|    2 | Ram  | 2007-05-27 |                220 |
|    3 | Jack | 2007-05-06 |                170 |
|    3 | Jack | 2007-04-06 |                100 |
|    4 | Jill | 2007-04-06 |                220 |
|    5 | Zara | 2007-06-06 |                300 |
|    5 | Zara | 2007-02-06 |                350 |
+------+------+------------+--------------------+
7 rows in set (0.00 sec)

现在，使用以下命令-

SQL> SELECT * FROM employee_tbl ORDER BY RAND();
+------+------+------------+--------------------+
| id   | name | work_date  | daily_typing_pages |
+------+------+------------+--------------------+
|    5 | Zara | 2007-06-06 |                300 |
|    3 | Jack | 2007-04-06 |                100 |
|    3 | Jack | 2007-05-06 |                170 |
|    2 | Ram  | 2007-05-27 |                220 |
|    4 | Jill | 2007-04-06 |                220 |
|    5 | Zara | 2007-02-06 |                350 |
|    1 | John | 2007-01-24 |                250 |
+------+------+------------+--------------------+
7 rows in set (0.01 sec)

SQL> SELECT * FROM employee_tbl ORDER BY RAND();
+------+------+------------+--------------------+
| id   | name | work_date  | daily_typing_pages |
+------+------+------------+--------------------+
|    5 | Zara | 2007-02-06 |                350 |
|    2 | Ram  | 2007-05-27 |                220 |
|    3 | Jack | 2007-04-06 |                100 |
|    1 | John | 2007-01-24 |                250 |
|    4 | Jill | 2007-04-06 |                220 |
|    3 | Jack | 2007-05-06 |                170 |
|    5 | Zara | 2007-06-06 |                300 |
+------+------+------------+--------------------+
7 rows in set (0.00 sec)

参考链接

https://www.learnfk.com/sql/sql-rand-function.html