greatest(n1,n2,n3,..........)greatest()函数返回输入参数(n1, n2, n3, 等)组的最大值。下面的示例使用 greatest()函数从一组数字值中返回最大的值：
mysql>select greatest(3,5,1,8,33,99,34,55,67,43);+---------------------------------------------------------+| greatest(3,5,1,8,33,99,34,55,67,43) |+---------------------------------------------------------+| 99 |+---------------------------------------------------------+1 row in set (0.00 sec)
住：greatest()函数是least()函数的相反函数。