這篇文章主要介紹了MySQL中的RAND()函數(shù)使用詳解,是MySQL入門學(xué)習(xí)中的基礎(chǔ)知識(shí),需要的朋友可以參考下

MySQL RAND()函數(shù)調(diào)用可以在0和1之間產(chǎn)生一個(gè)隨機(jī)數(shù)：
 

1. mysql> SELECT RAND( ), RAND( ), RAND( ); 
2. +------------------+-----------------+------------------+ 
3. | RAND( ) | RAND( ) | RAND( ) | 
4. +------------------+-----------------+------------------+ 
5. | 0.45464584925645 | 0.1824410643265 | 0.54826780459682 | 
6. +------------------+-----------------+------------------+ 
7. 1 row in set (0.00 sec) 

當(dāng)調(diào)用一個(gè)整數(shù)參數(shù)時(shí)，RAND()使用該隨機(jī)數(shù)發(fā)生器種子值。每次在給定值種子生成，RAND()會(huì)產(chǎn)生一個(gè)可重復(fù)的一系列數(shù)字：

可以使用ORDER BY RAND()，隨機(jī)組行或值如下：

要了解ORDER BY RAND()函數(shù), 假設(shè)EMPLOYEE_TBL的表有以下記錄：

1. mysql> SELECT * FROM employee_tbl; 
2. +------+------+------------+--------------------+ 
3. | id | name | work_date | daily_typing_pages | 
4. +------+------+------------+--------------------+ 
5. | 1 | John | 2007-01-24 | 250 | 
6. | 2 | Ram | 2007-05-27 | 220 | 
7. | 3 | Jack | 2007-05-06 | 170 | 
8. | 3 | Jack | 2007-04-06 | 100 | 
9. | 4 | Jill | 2007-04-06 | 220 | 
10. | 5 | Zara | 2007-06-06 | 300 | 
11. | 5 | Zara | 2007-02-06 | 350 | 
12. +------+------+------------+--------------------+ 
13. 7 rows in set (0.00 sec) 

現(xiàn)在使用以下目錄：

1. mysql> SELECT * FROM employee_tbl ORDER BY RAND(); 
2. +------+------+------------+--------------------+ 
3. | id | name | work_date | daily_typing_pages | 
4. +------+------+------------+--------------------+ 
5. | 5 | Zara | 2007-06-06 | 300 | 
6. | 3 | Jack | 2007-04-06 | 100 | 
7. | 3 | Jack | 2007-05-06 | 170 | 
8. | 2 | Ram | 2007-05-27 | 220 | 
9. | 4 | Jill | 2007-04-06 | 220 | 
10. | 5 | Zara | 2007-02-06 | 350 | 
11. | 1 | John | 2007-01-24 | 250 | 
12. +------+------+------------+--------------------+ 
13. 7 rows in set (0.01 sec) 
14.  
15. mysql> SELECT * FROM employee_tbl ORDER BY RAND(); 
16. +------+------+------------+--------------------+ 
17. | id | name | work_date | daily_typing_pages | 
18. +------+------+------------+--------------------+ 
19. | 5 | Zara | 2007-02-06 | 350 | 
20. | 2 | Ram | 2007-05-27 | 220 | 
21. | 3 | Jack | 2007-04-06 | 100 | 
22. | 1 | John | 2007-01-24 | 250 | 
23. | 4 | Jill | 2007-04-06 | 220 | 
24. | 3 | Jack | 2007-05-06 | 170 | 
25. | 5 | Zara | 2007-06-06 | 300 | 
26. +------+------+------------+--------------------+ 
27. 7 rows in set (0.00 sec)