【高频SQL基础50题】46-50

SQL时刻。

1.至少有5名直接下属的经理

2.确认率

[3.游戏玩法分析 IV](#3.游戏玩法分析 IV)

4.部门工资前三高的所有员工

5.查找拥有有效邮箱的用户

1.至少有5名直接下属的经理

子查询。

1.先找出至少有5名直接下属的经理号managerId

2.根据经理号找到对应名字

sql 复制代码

# Write your MySQL query statement below
select name
from Employee
where id in (
    select managerId
    from Employee
    group by managerId
    having count(managerId)>=5
)

2.确认率

左连接+子查询。

sql 复制代码

# Write your MySQL query statement below
select s.user_id,round(count(if(c.action='confirmed',1,null))/count(*),2) as confirmation_rate
from Signups s left join Confirmations c
on s.user_id=c.user_id
group by s.user_id;

3.游戏玩法分析 IV

先过滤出每个用户的首次登陆日期，然后左关联，筛选次日存在的记录的比例。

sql 复制代码

# Write your MySQL query statement below
select round(avg(a.event_date is not null),2) fraction
from 
(
    select player_id,min(event_date) as login
    from activity
    group by player_id
) p
left join activity a
on p.player_id=a.player_id and datediff(a.event_date,p.login)=1

ps:

4.部门工资前三高的所有员工

贴优秀题解。

sql 复制代码

# Write your MySQL query statement below
select Department.name as Department,
       e1.name as Employee,
       e1.salary as Salary
from Employee as e1,Department
where 
     e1.departmentId=Department.id
     and 3>(
            select count(distinct e2.Salary)
            from Employee as e2
            where e1.salary<e2.salary and e1.departmentId=e2.departmentId
)
order by Department.name,Salary desc;

5.查找拥有有效邮箱的用户

sql 复制代码

# Write your MySQL query statement below
#正则表达式，有意思
select t1.*
from Users t1
where t1.mail REGEXP '^[a-zA-Z][a-zA-Z0-9_\./\-]*\@leetcode[\.]com$';

ps:

有些字符需要转义。

一遍终于结束了！！！！！