MySQL UPDATE 随机数在 1-3 之间 [英] MySQL UPDATE with random number between 1-3

问题描述

有一张大表，我想添加一列，其中每条记录都有一个随机选择的数字.1、2 或 3.

Got a big table and I want to add a column that has a randomly chosen number for each record. 1, 2, or 3.

很难过.有什么想法吗?

Having a hard time. Any ideas?

推荐答案

试试这个:

UPDATE tableName SET columnName = FLOOR( 1 + RAND( ) *3 );

来自 MySQL 文档 <代码>兰德:

From the MySQL documentation for RAND:

返回 0 <= v

Returns a random floating-point value v in the range 0 <= v < 1.0.

所以在上面的查询中，1 + RAND()*3 可以生成的最大值将是 3.999999，当取底时会给出 3.当 RAND() 返回 0 时会出现最小值，在这种情况下会给出 1.

So in the above query, the largest value which could be generated by 1 + RAND()*3 would be 3.999999, which when floored would give 3. The smallest value would occur when RAND() returns 0, in which case this would give 1.

这篇关于MySQL UPDATE 随机数在 1-3 之间的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！