mysql 生成随机数rand()

mysql> select rand();
+--------------------+
| rand()             |
+--------------------+
| 0.9913473352709294 |
+--------------------+
 row in set (0.00 sec)

mysql> select rand()*;
+-------------------+
| rand()*        |
+-------------------+
| 57.10881106286199 |
+-------------------+
 row in set (0.01 sec)