【篮球世界杯赌球】MySQL中的RAND()函数使用详解

2020-04-03 04:50 来源:未知

MySQL RAND()函数调用可以在0和1之间产生一个随机数:

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

当调用一个整数参数时,RAND()使用该随机数发生器种子值。每次在给定值种子生成,RAND()会产生一个可重复的一系列数字:

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

可以使用ORDER BY RAND(),随机组行或值如下:

要了解ORDER BY RAND()函数, 假设EMPLOYEE_TBL的表有以下记录:

mysql 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)

现在使用以下目录:

mysql 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)mysql 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)
TAG标签:
版权声明:本文由美洲杯赌球发布于计算机教程,转载请注明出处:【篮球世界杯赌球】MySQL中的RAND()函数使用详解