27_MySQL数字函数（重点）

/*
SALES部门中工龄超过20年的，底薪增加10%
SALES部门中工龄不满20年的，底薪增加5%
ACCOUNTING部门，底薪增加300元
RESEARCH部门里低于部门平均底薪的，底薪增加200元
没有部门的员工，底薪增加100元
*/

UPDATE t_emp e1 LEFT JOIN t_dept d1 ON e1.deptno = d1.deptno
LEFT JOIN (SELECT e.deptno AS deptno,AVG( e.sal ) AS avg
FROM t_emp e LEFT JOIN t_dept d ON e.deptno = d.deptno AND d.dname = "RESEARCH" ) t
ON e1.deptno = t.deptno
SET e1.sal = (
CASE
    WHEN d1.dname = "SALES" AND DATEDIFF( NOW( ), hiredate ) / 365 >= 20 THEN e1.sal * 1.1
    WHEN d1.dname = "SALES" AND DATEDIFF( NOW( ), hiredate ) / 365 > 20 THEN e1.sal * 1.05
    WHEN d1.dname = "ACCOUNTING" THEN e1.sal + 300
    WHEN e1.sal <= t.avg THEN e1.sal + 200
    WHEN e1.deptno IS NULL THEN e1.sal + 100
    ELSE e1.sal
    END
);
)