数据库原理及应用-李唯唯主编-实验3-2

实验3-2

一、实验目的与要求

1. 掌握单表查询
2. 掌握多表连接查询
3. 掌握子查询、集合查询。
4. 掌握派生表查询。
5. 掌握聚合函数使用方法

二、实验内容

1. 实验平台：
   • 操作系统：windows11
   • 数据库：MySQL8
   • 数据库管理平台：Navicat Premium 15
2. 在数据库supermarket上完成下列操作
   1. 查询商品种类信息。
   2. 查询IT专业所有学生信息。
   3. 查询MIS专业年龄小于20岁的学生信息。并为MIS列取别名为 “信息管理系统”
   4. 查询利润率大于30%的商品编号与商品名。
   5. 查询广州佛山供应的商品信息。
   6. 查询购买了商品种类为咖啡的MIS专业的学生信息。
   7. 查询购买了商品种类为咖啡的各专业的学生人数。
   8. 查询购买各商品种类的各专业的学生人数。
   9. 查询从未购买过商品的学生信息。
   10. 查询与商品编号GN0005相同产地的商品编号、商品名。
   11. 使用派生表查询各供应商的存货量。
   12. 查询售价大于该种类商品售价均值的商品号、商品名。
   13. 分别用子查询 与 连接查询查询购买了商品编号为 “GN0003” 和"GN0007"的学生学号与姓名。
   14. 查询各校销售额。
   15. 查询购买额前三的校名、专业名。
   16. 使用集合查询方式查询生产日期早于2018-1-1 或 库存量小于30的商品信息。

三、实验过程、步骤及结果

1. 题目：查询商品种类信息

   • 代码：

     -- 实验3-2
     -- 1. 查询商品种类信息。
     -- 方法一
     SELECT * FROM category;
     -- 方法二
     SELECT CategoryNO 编号,CategoryName 种类,Description 具体描述 FROM category;
     
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-BblEH3J7-1665624066603)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161526838.png)]

2. ---

   题目：查询IT专业所有学生信息

   • 代码：

     -- 2. 查询IT专业所有学生信息。
     -- 方法一
     SELECT * FROM student WHERE Major = 'IT';
     
     -- 方法二
     SELECT SNO 学号,SName 姓名,BirthYear 出生年份,Ssex 性别,College 学院,Major 专业,WeiXin 专业 FROM student WHERE Major = 'IT';
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-GGWM1ikz-1665624066604)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161543809.png)]

3. ---

   题目：查询MIS专业年龄小于20岁的学生信息。并为MIS列取别名为 “信息管理系统”

   • 代码：

     -- 3. 查询MIS专业且年龄小于20岁的学生信息。并为MIS列取别名为 "信息管理系统"。
     -- 第一次查询不到信息，因为这里的BirthYear不是date类型，而是int，类型，所以直接减就行了SELECT * FROM student WHERE Major = 'MIS' AND (YEAR(NOW())-YEAR(BirthYear)) > 20;
     -- 第一次查询不到信息，因为这里的BirthYear都已经超过了20岁，所以找不到满足条件的，因此查询MIS专业且年龄大于20岁的学生信息
     -- 方法一:查询MIS专业且年龄小于20岁的学生信息
     SELECT * FROM student WHERE Major = 'MIS' AND (YEAR(NOW())-BirthYear) < 20;
     
     -- 方法二:查询MIS专业且年龄大于20岁的学生信息
     SELECT SNO 学号,SName 姓名,BirthYear 出生年份,(YEAR(NOW())-BirthYear) 年龄,Ssex 性别,College 学院,Major 专业,WeiXin 专业 FROM student WHERE Major = 'MIS' AND (YEAR(NOW())-BirthYear) > 20;
     
     
     
     -- 方法二
     SELECT SNO 学号,SName 姓名,BirthYear 出生年份,Ssex 性别,College 学院,Major 专业,WeiXin 专业 FROM student WHERE Major = 'IT';
     
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-gf5ntqBy-1665624066604)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161617075.png)][外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-GYUeu6Yd-1665624066605)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161632448.png)]

4. ---

   题目：查询利润率大于30%的商品编号与商品名

   • 代码：

     -- 4. 查询利润率大于30%的商品编号与商品名。
     -- SELECT * FROM goods WHERE (SalePrice-InPrice)/InPrice < 0.3;
     SELECT GoodsNO 商品编号,GoodsName 商品名,ROUND((SalePrice-InPrice)/InPrice,2) AS 利润率 FROM goods WHERE (SalePrice-InPrice)/InPrice < 0.3;
     SELECT GoodsNO 商品编号,GoodsName 商品名,ROUND((SalePrice-InPrice)/InPrice,2) AS 利润率 FROM goods WHERE (SalePrice-InPrice)/InPrice > 0.3;
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-loYhYfgu-1665624066605)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161901957.png)][外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-d7jvMRkU-1665624066605)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161913598.png)]

5. ---

   题目：查询广州佛山供应的商品信息

   • 代码：

     -- 5. 查询广州佛山供应的商品信息。
     SELECT g.GoodsNO 商品编号,s.SupplierNO 供应商编号,g.CategoryNO 商品种类编号,g.GoodsName 商品名,s.Address 供应商,s.SupplierName 公司  FROM goods g
     LEFT JOIN supplier s ON g.SupplierNO = s.SupplierNO
     WHERE s.Address = '广州佛山';
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-4Z9XxBR0-1665624066605)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161941446.png)]

6. ---

   题目：查询购买了商品种类为咖啡的MIS专业的学生信息

   • 代码：

     -- 6. 查询购买了商品种类为咖啡的MIS专业的学生信息。
     -- 方法一:使用子查询语句
     SELECT * FROM student st WHERE SNO IN(
     	SELECT SNO FROM salebill WHERE GoodsNO IN (
     		SELECT GoodsNO 
     		FROM category c
     		LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
     		WHERE c.CategoryName = '咖啡')) 
     AND Major = 'MIS'
     
     -- 方法2:使用左右外连接
     SELECT DISTINCT st.SNO,st.SName,st.BirthYear,st.Ssex,st.College,st.Major,st.WeiXin 
     FROM category c
     LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
     LEFT JOIN salebill s ON s.GoodsNO = g.GoodsNO
     LEFT JOIN student st ON st.SNO = s.SNO
     WHERE c.CategoryName = '咖啡' AND st.Major='MIS';
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-KENkiepN-1665624066606)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012161959760.png)]

7. ---

   题目：查询购买了商品种类为咖啡的各专业的学生人数

   • 代码：

     -- 7. 查询购买了商品种类为咖啡的各专业的学生人数。
     -- 方法一:使用子查询语句
     SELECT Major 专业,COUNT(Major) 人数 FROM student st WHERE SNO IN(
     	SELECT SNO FROM salebill WHERE GoodsNO IN (
     		SELECT GoodsNO 
     		FROM category c
     		LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
     		WHERE c.CategoryName = '咖啡'))  
     GROUP BY Major;
     
     -- 方法二:使用左右外连接
     SELECT sc.Major 专业,COUNT(sc.Major) 人数 
     FROM student st
     RIGHT JOIN (
     		SELECT DISTINCT st.SNO,st.SName,st.BirthYear,st.Ssex,st.College,st.Major,st.WeiXin 
     		FROM category c
     		LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
     		LEFT JOIN salebill s ON s.GoodsNO = g.GoodsNO
     		right JOIN student st ON st.SNO = s.SNO
     WHERE c.CategoryName = '咖啡') sc ON st.SNO = sc.SNO
     GROUP BY sc.Major;
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-k5V5FlzD-1665624066606)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012162027303.png)]

8. ---

   题目： 查询购买各商品种类的各专业的学生人数

   • 代码：

     -- 8. 查询购买各商品种类的各专业的学生人数。
     -- 方法一:使用子查询语句
     SELECT Major,COUNT(Major) FROM student WHERE SNO IN (
     	SELECT DISTINCT SNO FROM salebill WHERE GoodsNO IN (
     		SELECT GoodsNO FROM goods WHERE CategoryNO IN (
     			SELECT CategoryNO FROM category))
     )
     GROUP BY Major;
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-B5lFf5wK-1665624066606)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012162056489.png)]

9. ---

   题目：查询从未购买过商品的学生信息

   • 代码：

     -- 9. 查询从未购买过商品的学生信息。
     -- 方法一:使用子查询语句
     SELECT * FROM student WHERE SNO NOT IN (
     	SELECT DISTINCT SNO FROM salebill WHERE GoodsNO IN (
     		SELECT GoodsNO FROM goods WHERE CategoryNO IN (
     			SELECT CategoryNO FROM category))
     );
     

   • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-8D1HWQ3o-1665624066607)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012162116300.png)]

10. ---

    题目： 查询与商品编号GN0005相同产地的商品编号、商品名

    • 代码：

      -- 10. 查询与商品编号GN0005相同产地的商品编号、商品名。
      -- 第一步:查询到商品编号GN0005商品的产地
      SELECT Address 
      FROM goods g
      LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO
      WHERE g.GoodsNO = 'GN0005';
      
      -- 第二步:根据商品的产地查询到供应商的编号
      SELECT SupplierNO FROM
      supplier
      WHERE Address = (
      	SELECT Address 
      	FROM goods g
      	LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO
      	WHERE g.GoodsNO = 'GN0005'
      )
      
      -- 第三步:使用子查询
      SELECT * FROM goods WHERE SupplierNO IN(
      	SELECT SupplierNO FROM supplier WHERE Address = (
      		SELECT Address 
      		FROM goods g
      		LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO
      		WHERE g.GoodsNO = 'GN0005')
      )
      

    • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-IKOs1FdJ-1665624066607)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012162446667.png)]

11. ---

    题目：使用派生表查询各供应商的存货量

    • 代码：

      -- 11. 使用派生表查询各供应商的存货量。
      SELECT sp.SupplierNO 供应商编号,sp.SupplierName 供应商名称,sg.sum_number 存货量 
      FROM supplier sp
      LEFT JOIN (SELECT SupplierNO,SUM(Number) sum_number FROM goods GROUP BY SupplierNO) sg
      ON sp.SupplierNO = sg.SupplierNO;
      

    • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-xPiwk85n-1665624066609)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012164131110.png)]

12. ---

    题目：查询售价大于该种类商品售价均值的商品号、商品名

    • 代码：

      -- 12. 查询售价大于该种类商品售价均值的商品号、商品名。
      -- 第一步:按种类分组求平均售价(保留小数点后两位)
      SELECT CategoryNO,(ROUND(AVG(SalePrice),2)) avg_saleprice FROM goods
      GROUP BY CategoryNO;
      
      SELECT g.GoodsNO 商品编号,g.SupplierNO 供应商编号, sg.CategoryNO 商品种类编号,g.GoodsName 商品名,g.SalePrice 售价,sg.avg_saleprice 该类商品的平均售价 
      FROM goods g
      right JOIN (
      	SELECT
      		CategoryNO,
      		ROUND(AVG( SalePrice ),2) avg_saleprice 
      	FROM
      		goods 
      	GROUP BY
      	CategoryNO) sg
      ON g.CategoryNO = sg.CategoryNO AND g.SalePrice > sg.avg_saleprice;
      

    • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-J7F2yrRB-1665624066609)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012165213442.png)]

13. ---

    题目：分别用子查询 与 连接查询查询购买了商品编号为 “GN0003” 和"GN0007"的学生学号与姓名

    • 代码：

      -- 13. 分别用子查询 与 连接查询查询购买了商品编号为 "GN0003" 和"GN0007"的学生学号与姓名。
      -- 方法一:使用子查询
      SELECT SNO,SName FROM student WHERE SNO IN(
      		SELECT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007'
      )
      
      SELECT SNO,SName FROM student WHERE SNO IN(
      		SELECT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007' GROUP BY SNO HAVING COUNT(GoodsNO) = 2
      )
      
      -- 方法二:使用连接查询
      SELECT st.SNO,st.SName 
      FROM student st
      RIGHT JOIN (
      	 SELECT DISTINCT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007') g
      ON st.SNO = g.SNO
      ORDER BY st.SNO ASC
      
      SELECT st.SNO,st.SName 
      FROM student st
      RIGHT JOIN (
      	 SELECT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007' GROUP BY SNO HAVING COUNT(GoodsNO) = 2) g
      ON st.SNO = g.SNO
      ORDER BY st.SNO ASC
      

    • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-xGm3rgJ9-1665624066610)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221012170149140.png)][外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-u5EpgkEm-1665624066610)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221013084331224.png)]

14. ---

    题目：查询各校销售额

    • 代码：

      -- 14. 查询各校销售额。
      -- 第一步:计算各个学生的销售额
      SELECT s.SNO s_SNO ,SUM((s.Number*g.SalePrice)) sum_number_price FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO;
      -- 第二步:计算各校的销售数量
      SELECT st.College 学校,SUM(sg.sum_number_price) 销售额
      FROM student st
      LEFT JOIN (
      	SELECT s.SNO s_SNO ,SUM((s.Number*g.SalePrice)) sum_number_price FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO
      ) sg
      ON st.SNO = sg.s_SNO
      GROUP BY College;
      
      -- 14. 查询各公司销售额。
      -- 第一步:计算各类商品的销售数量
      SELECT GoodsNO,SUM(Number) sum_number FROM salebill
      GROUP BY GoodsNO;
      
      SELECT sg.GoodsNO,g.GoodsName,sp.SupplierName 公司,g.SalePrice*sg.sum_number 销售额 FROM goods g
      RIGHT JOIN (SELECT GoodsNO,SUM(Number) sum_number FROM salebill
      GROUP BY GoodsNO) sg
      ON g.GoodsNO = sg.GoodsNO
      LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO;
      

    • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-UvHxMooL-1665624066611)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221013084042608.png)][外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-hCFUwgIX-1665624066612)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221013084133433.png)]

15. ---

    题目：查询销售额、购买额前三的校名、专业名

    • 代码：

      -- 15. 查询销售额、购买额前三的校名、专业名。
      SELECT st.College 学校,Major 专业名,SUM(sg.sum_number_price) 销售额
      FROM student st
      LEFT JOIN (
      	SELECT s.SNO s_SNO ,SUM((s.Number*g.SalePrice)) sum_number_price FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO
      ) sg
      ON st.SNO = sg.s_SNO
      GROUP BY College,Major
      ORDER BY Major DESC
      LIMIT 0,3;
      
      SELECT st.College 学校,Major 专业名,SUM(sg.sum_number) 购买额
      FROM student st
      LEFT JOIN (
      	SELECT s.SNO s_SNO ,SUM(s.Number) sum_number FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO
      ) sg
      ON st.SNO = sg.s_SNO
      GROUP BY College,Major
      ORDER BY Major DESC
      LIMIT 0,3;
      

    • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-hBuQt7OR-1665624066612)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221013083645807.png)][外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-6isjtRii-1665624066613)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221013084011868.png)]

16. ---

    题目：使用集合查询方式查询生产日期早于2018-1-1 或 库存量小于30的商品信息

    • 代码：

      -- 16. 使用集合查询方式查询生产日期早于2018-1-1 或 库存量小于30的商品信息。
      -- 方法一:使用union
      SELECT * FROM goods WHERE DATEDIFF(DATE(ProductTime),'2018-1-1') < 0
      UNION
      SELECT * FROM goods WHERE QGPeriod < 30;
      -- 
      SELECT GoodsNO,SupplierNO,CategoryNO,GoodsName,InPrice,SalePrice,Number,ProductTime 生产日期,QGPeriod 库存,DATEDIFF(DATE(ProductTime),'2018-1-1') 日期差  
      FROM goods 
      WHERE DATEDIFF(DATE(ProductTime),'2018-1-1') < 0 OR QGPeriod < 30;
      

    • 效果图：[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-7u2WB6Dm-1665624066613)(C:\Users\SayHello\AppData\Roaming\Typora\typora-user-images\image-20221013083624345.png)]

四、具体查询

-- 实验3-2
-- 1. 查询商品种类信息。
-- 方法一
SELECT * FROM category;
-- 方法二
SELECT CategoryNO 编号,CategoryName 种类,Description 具体描述 FROM category;



-- 2. 查询IT专业所有学生信息。
-- 方法一
SELECT * FROM student WHERE Major = 'IT';

-- 方法二
SELECT SNO 学号,SName 姓名,BirthYear 出生年份,Ssex 性别,College 学院,Major 专业,WeiXin 专业 FROM student WHERE Major = 'IT';



-- 3. 查询MIS专业且年龄小于20岁的学生信息。并为MIS列取别名为 "信息管理系统"。
-- 第一次查询不到信息，因为这里的BirthYear不是date类型，而是int，类型，所以直接减就行了SELECT * FROM student WHERE Major = 'MIS' AND (YEAR(NOW())-YEAR(BirthYear)) > 20;
-- 第一次查询不到信息，因为这里的BirthYear都已经超过了20岁，所以找不到满足条件的，因此查询MIS专业且年龄大于20岁的学生信息
-- 方法一:查询MIS专业且年龄小于20岁的学生信息
SELECT * FROM student WHERE Major = 'MIS' AND (YEAR(NOW())-BirthYear) < 20;

-- 方法二:查询MIS专业且年龄大于20岁的学生信息
SELECT SNO 学号,SName 姓名,BirthYear 出生年份,(YEAR(NOW())-BirthYear) 年龄,Ssex 性别,College 学院,Major 专业,WeiXin 专业 FROM student WHERE Major = 'MIS' AND (YEAR(NOW())-BirthYear) > 20;


-- 4. 查询利润率大于30%的商品编号与商品名。
-- SELECT * FROM goods WHERE (SalePrice-InPrice)/InPrice < 0.3;
SELECT GoodsNO 商品编号,GoodsName 商品名,ROUND((SalePrice-InPrice)/InPrice,2) AS 利润率 FROM goods WHERE (SalePrice-InPrice)/InPrice < 0.3;
SELECT GoodsNO 商品编号,GoodsName 商品名,ROUND((SalePrice-InPrice)/InPrice,2) AS 利润率 FROM goods WHERE (SalePrice-InPrice)/InPrice > 0.3;

-- 5. 查询广州佛山供应的商品信息。
SELECT g.GoodsNO 商品编号,s.SupplierNO 供应商编号,g.CategoryNO 商品种类编号,g.GoodsName 商品名,s.Address 供应商,s.SupplierName 公司  FROM goods g
LEFT JOIN supplier s ON g.SupplierNO = s.SupplierNO
WHERE s.Address = '广州佛山';

-- 6. 查询购买了商品种类为咖啡的MIS专业的学生信息。
-- 方法一:使用子查询语句
SELECT * FROM student st WHERE SNO IN(
	SELECT SNO FROM salebill WHERE GoodsNO IN (
		SELECT GoodsNO 
		FROM category c
		LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
		WHERE c.CategoryName = '咖啡')) 
AND Major = 'MIS'

-- 方法2:使用左右外连接
SELECT DISTINCT st.SNO,st.SName,st.BirthYear,st.Ssex,st.College,st.Major,st.WeiXin 
FROM category c
LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
LEFT JOIN salebill s ON s.GoodsNO = g.GoodsNO
LEFT JOIN student st ON st.SNO = s.SNO
WHERE c.CategoryName = '咖啡' AND st.Major='MIS';
	

-- 7. 查询购买了商品种类为咖啡的各专业的学生人数。
-- 方法一:使用子查询语句
SELECT Major 专业,COUNT(Major) 人数 FROM student st WHERE SNO IN(
	SELECT SNO FROM salebill WHERE GoodsNO IN (
		SELECT GoodsNO 
		FROM category c
		LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
		WHERE c.CategoryName = '咖啡'))  
GROUP BY Major;

-- 方法二:使用左右外连接
SELECT sc.Major 专业,COUNT(sc.Major) 人数 
FROM student st
RIGHT JOIN (
		SELECT DISTINCT st.SNO,st.SName,st.BirthYear,st.Ssex,st.College,st.Major,st.WeiXin 
		FROM category c
		LEFT JOIN goods g ON c.CategoryNO = g.CategoryNO
		LEFT JOIN salebill s ON s.GoodsNO = g.GoodsNO
		right JOIN student st ON st.SNO = s.SNO
WHERE c.CategoryName = '咖啡') sc ON st.SNO = sc.SNO
GROUP BY sc.Major;


-- 8. 查询购买各商品种类的各专业的学生人数。
-- 方法一:使用子查询语句
SELECT Major,COUNT(Major) FROM student WHERE SNO IN (
	SELECT DISTINCT SNO FROM salebill WHERE GoodsNO IN (
		SELECT GoodsNO FROM goods WHERE CategoryNO IN (
			SELECT CategoryNO FROM category))
)
GROUP BY Major;

-- 9. 查询从未购买过商品的学生信息。
-- 方法一:使用子查询语句
SELECT * FROM student WHERE SNO NOT IN (
	SELECT DISTINCT SNO FROM salebill WHERE GoodsNO IN (
		SELECT GoodsNO FROM goods WHERE CategoryNO IN (
			SELECT CategoryNO FROM category))
);


-- 10. 查询与商品编号GN0005相同产地的商品编号、商品名。
-- 第一步:查询到商品编号GN0005商品的产地
SELECT Address 
FROM goods g
LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO
WHERE g.GoodsNO = 'GN0005';

-- 第二步:根据商品的产地查询到供应商的编号
SELECT SupplierNO FROM
supplier
WHERE Address = (
	SELECT Address 
	FROM goods g
	LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO
	WHERE g.GoodsNO = 'GN0005'
)

-- 第三步:使用子查询
SELECT * FROM goods WHERE SupplierNO IN(
	SELECT SupplierNO FROM supplier WHERE Address = (
		SELECT Address 
		FROM goods g
		LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO
		WHERE g.GoodsNO = 'GN0005')
)


-- 11. 使用派生表查询各供应商的存货量。
SELECT sp.SupplierNO 供应商编号,sp.SupplierName 供应商名称,sg.sum_number 存货量 
FROM supplier sp
LEFT JOIN (SELECT SupplierNO,SUM(Number) sum_number FROM goods GROUP BY SupplierNO) sg
ON sp.SupplierNO = sg.SupplierNO;



-- 12. 查询售价大于该种类商品售价均值的商品号、商品名。
-- 第一步:按种类分组求平均售价(保留小数点后两位)
SELECT CategoryNO,(ROUND(AVG(SalePrice),2)) avg_saleprice FROM goods
GROUP BY CategoryNO;

SELECT g.GoodsNO 商品编号,g.SupplierNO 供应商编号, sg.CategoryNO 商品种类编号,g.GoodsName 商品名,g.SalePrice 售价,sg.avg_saleprice 该类商品的平均售价 
FROM goods g
right JOIN (
	SELECT
		CategoryNO,
		ROUND(AVG( SalePrice ),2) avg_saleprice 
	FROM
		goods 
	GROUP BY
	CategoryNO) sg
ON g.CategoryNO = sg.CategoryNO AND g.SalePrice > sg.avg_saleprice;


-- 13. 分别用子查询 与 连接查询查询购买了商品编号为 "GN0003" 和"GN0007"的学生学号与姓名。
-- 方法一:使用子查询
SELECT SNO,SName FROM student WHERE SNO IN(
		SELECT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007'
)

SELECT SNO,SName FROM student WHERE SNO IN(
		SELECT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007' GROUP BY SNO HAVING COUNT(GoodsNO) = 2
)

-- 方法二:使用连接查询
SELECT st.SNO,st.SName 
FROM student st
RIGHT JOIN (
	 SELECT DISTINCT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007') g
ON st.SNO = g.SNO
ORDER BY st.SNO ASC

SELECT st.SNO,st.SName 
FROM student st
RIGHT JOIN (
	 SELECT SNO FROM salebill WHERE GoodsNO = 'GN0003' OR GoodsNO = 'GN0007' GROUP BY SNO HAVING COUNT(GoodsNO) = 2) g
ON st.SNO = g.SNO
ORDER BY st.SNO ASC


-- 14. 查询各校销售额。
-- 第一步:计算各个学生的销售额
SELECT s.SNO s_SNO ,SUM((s.Number*g.SalePrice)) sum_number_price FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO;
-- 第二步:计算各校的销售数量
SELECT st.College 学校,SUM(sg.sum_number_price) 销售额
FROM student st
LEFT JOIN (
	SELECT s.SNO s_SNO ,SUM((s.Number*g.SalePrice)) sum_number_price FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO
) sg
ON st.SNO = sg.s_SNO
GROUP BY College;

SELECT GoodsNO,SUM(Number) sum_number FROM salebill
GROUP BY GoodsNO;

SELECT sg.GoodsNO,g.GoodsName,sp.SupplierName 公司,g.SalePrice*sg.sum_number 销售额 FROM goods g
RIGHT JOIN (SELECT GoodsNO,SUM(Number) sum_number FROM salebill
GROUP BY GoodsNO) sg
ON g.GoodsNO = sg.GoodsNO
LEFT JOIN supplier sp ON g.SupplierNO = sp.SupplierNO;


-- 15. 查询销售额、购买额前三的校名、专业名。
SELECT st.College 学校,Major 专业名,SUM(sg.sum_number_price) 销售额
FROM student st
LEFT JOIN (
	SELECT s.SNO s_SNO ,SUM((s.Number*g.SalePrice)) sum_number_price FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO
) sg
ON st.SNO = sg.s_SNO
GROUP BY College,Major
ORDER BY Major DESC
LIMIT 0,3;

SELECT st.College 学校,Major 专业名,SUM(sg.sum_number) 购买额
FROM student st
LEFT JOIN (
	SELECT s.SNO s_SNO ,SUM(s.Number) sum_number FROM salebill s LEFT JOIN goods g ON s.GoodsNO = g.GoodsNO GROUP BY SNO
) sg
ON st.SNO = sg.s_SNO
GROUP BY College,Major
ORDER BY Major DESC
LIMIT 0,3;


-- 16. 使用集合查询方式查询生产日期早于2018-1-1 或 库存量小于30的商品信息。
-- 方法一:使用union
SELECT * FROM goods WHERE DATEDIFF(DATE(ProductTime),'2018-1-1') < 0
UNION
SELECT * FROM goods WHERE QGPeriod < 30;
-- 
SELECT GoodsNO,SupplierNO,CategoryNO,GoodsName,InPrice,SalePrice,Number,ProductTime 生产日期,QGPeriod 库存,DATEDIFF(DATE(ProductTime),'2018-1-1') 日期差  
FROM goods 
WHERE DATEDIFF(DATE(ProductTime),'2018-1-1') < 0 OR QGPeriod < 30;

数据库文件:>
supermarket.sql
https://www.aliyundrive.com/s/hmXsCqZJHN3
提取码: 4rx3
点击链接保存，或者复制本段内容，打开「阿里云盘」APP ，无需下载极速在线查看，视频原画倍速播放。

查询语句文件:>
实验3-2.sql
https://www.aliyundrive.com/s/vshDT2MhVnG
提取码: 3x1e
点击链接保存，或者复制本段内容，打开「阿里云盘」APP ，无需下载极速在线查看，视频原画倍速播放。

五、实验总结

1. 综合考查了对数据库表的查询的DML语句，单表查询、多表联查的使用
2. 综合考查了子查询语句、集合查询、派生查询的具体应用
3. 综合考查了聚合函数、分组查询、limit子句的知识