1.181超过经理的员工-简单
select a.name as "Employee" from Employee a, Employee b
where a.managerId = b.id
and a.salary > b.salary
2.182查找重复的电子邮箱-简单
1)Email和count(Email)作为临时表,再使用where
2)group by+having count>1
(where>group by>having>order by)
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3.183从不订购的客户-简单
1)not in
2)left join
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4.184部门工资最高的员工-中等
步骤一:使用group by+max函数查询每个部门的最高工资
步骤二:连接Employee表和Department表
5.185部门工资前三高的所有员工-困难
1)where子句统计每个部门前三高工资员工+连接Employee和Department表
2)dense_rank() over
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