select 	p.Name,p.Statisfaction,d.Departmentfrom 	Person as pinner join (select                d.DepartmentID,d.Department, max(p.Statisfaction) as Statisfaction            from                 Department as d            left join Person as p            on p.DepartmentID = d.DepartmentID            group by d.DepartmentID,d.Department) as don p.Statisfaction = d.Statisfaction and p.DepartmentID = d.DepartmentIDorder by d.DepartmentID-- 先查出每个部门的最高满意度、部门ID、部门名称，然后和员工表做一个内连接

select     distinct c.id,c.phone,c.call_datefrom(select          a.*,DATEDIFF("D",a.Call_date,b.Call_date) as daydiff     from Call as a,Call as b     where a.Phone = b.Phone and a.id != b.id) as cwhere c.daydiff >=0 and c.daydiff <= 7-- 自连接