create table jobs(
    id INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
        .....
        salaryminus INTEGER UNSIGNED DEFAULT NULL,
        salaryplus INTEGER UNSIGNED DEFAULT NULL,
        .....
);

现在想要实现类似：

Select * from jobs order by maxof(salaryminus, salaryplus) limit 10;

其中maxof(Null,1000)应该等于1000