MySQL 特殊运算符

select greatest(2,0),greatest(20.0,3.0,100.5),greatest('a','b','c'),greatest(10,NULL);
greatest(x,y,z)
select least(2,0),least(20.0,3.0,100.5),least('a','b','c'),least(10,NULL);
least(x,y,z)
REGEXP(x,y,z)
select 'ssky' regexp '^s', 'ssky' regexp 'y$', 'ssky' regexp '.sky', 'ssky' regexp '[ab]';