MySQL UPDATE，随机数介于1-3之间 [英] MySQL UPDATE with random number between 1-3

问题描述

有一个大表，我想添加一列，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.有什么想法吗?

推荐答案

尝试一下:

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

从MySQL 文档中，RAND:

返回范围0< = v<中的随机浮点值v. 1.0.

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

因此，在上面的查询中，1 + RAND()*3可能生成的最大值为3.999999，在下限时为3.最小值在RAND()返回0时出现，在这种情况下，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.

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