目录

1.上级经理已离职的公司员工

2.修复表中的名字 

3. 寻找用户推荐人

4.产品销售分析 I 

5.平均售价

1.上级经理已离职的公司员工

 子查询。

先根据薪水大小查询，再根据manager_id查询该员工是否存在，最后做排序。

# Write your MySQL query statement below
SELECT 
    employee_id
FROM 
    Employees
WHERE 
    salary<30000
AND 
    manager_id not in (SELECT employee_id employee_id FROM Employees)
ORDER BY
    employee_id

2.修复表中的名字 

SQL语句的使用 

 

# Write your MySQL query statement below
#重命名为name
SELECT user_id,CONCAT(UPPER(SUBSTRING(name,1,1)),LOWER(SUBSTRING(name,2))) name
FROM Users
ORDER BY user_id

3. 寻找用户推荐人

 

查询题。

# Write your MySQL query statement below
SELECT name FROM customer
WHERE id NOT IN
(SELECT id FROM customer WHERE referee_id=2);

 

4.产品销售分析 I 

 

连接题。

 

# Write your MySQL query statement below
SELECT p.product_name,s.year,s.price
FROM Sales s
LEFT JOIN Product p
ON s.product_id=p.product_id

5.平均售价

 

聚合函数题。

# Write your MySQL query statement below
SELECT p.product_id,ROUND(SUM(p.price*u.units)/SUM(u.units),2)
AS average_price FROM Prices AS p
JOIN UnitsSold AS u
ON p.product_id=u.product_id
AND u.purchase_date BETWEEN p.start_date AND p.end_date
GROUP BY p.product_id 
UNION ALL SELECT product_id, 0 AS average_price FROM Prices WHERE product_id NOT IN ( SELECT DISTINCT product_id FROM UnitsSold )