#关系运算符（<>=!not）与逻辑运算符（&and|or）set @x=7,@y=5;select @x>=@y as 'TRUE',@x<=@y as 'FALSE';#正确返回值true,实际返回值1，false=0select @x=@y;# 判断两个数值是否相等无需使用（==）号，使用（=）即可。#逻辑运算符select TRUE AND TRUE；select FALSE OR TRUE；#使用变量参与实际的查询（增删改）操作set @userName='龙姑娘，王语嫣，赵灵儿';set @age=17;select * from student where userName=@userName or age=@age;#多个同列信息查询inselect @userName;#无法识别关键数字以及符号set @userName1='龙姑娘';set @userName2='王语嫣';set @userName3='赵灵儿';select * from student where userName in（@userName1，@userName2，@userName3);