MySQL UPDATE 随机数在 1-3 之间
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MySQL UPDATE with random number between 1-3
提问by karnival8
Got a big table and I want to add a column that has a randomly chosen number for each record. 1, 2, or 3.
有一个大表，我想为每条记录添加一个随机选择的数字的列。1、2 或 3。
Having a hard time. Any ideas?
过得很艰难。有任何想法吗？
回答by Rabbie
Try this:
尝试这个：
UPDATE tableName SET columnName = FLOOR( 1 + RAND( ) *3 );
From the MySQL documentationfor RAND:
从MySQL文档为RAND：
Returns a random floating-point value v in the range 0 <= v < 1.0.
返回范围 0 <= v < 1.0 内的随机浮点值 v。
So in the above query, the largest value which could be generated by 1 + RAND()*3would 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.
所以在上面的查询中，可以生成的最大值1 + RAND()*3是3.999999，当 floored 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。
回答by Faisal
Use RAND()function. It returns a random floating-point value v in the range 0 <= v < 1.0. To obtain a random integer R in the range i <= R < j, use the expression FLOOR(i + RAND() * (j ? i + 1)). For example, to obtain a random integer in the range the range 1<= R < 3, use the following statement:
使用RAND()函数。它返回范围内的随机浮点值 v 0 <= v < 1.0。要获得范围内的随机整数 R i <= R < j，请使用表达式FLOOR(i + RAND() * (j ? i + 1))。例如，要获取 range 范围内的随机整数1<= R < 3，请使用以下语句：
UPDATE tableName
SET ColumnName= FLOOR(1 + rand() * 3);
N.B :RAND()produces random float values from 0 to 1.
注意：RAND()产生从 0 到 1 的随机浮点值。
回答by facuap
Do this
做这个
UPDATE tableName SET columnName = FLOOR(RAND( ) + RAND( ));
