MySQL 练习题3

1.创建表结构和表数据

-- 创建数据表
  CREATE TABLE IF NOT EXISTS tdb_goods(
    goods_id    SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT, -- 商品主键
    goods_name  VARCHAR(150) NOT NULL,    -- 商品名称
    goods_cate  VARCHAR(40)  NOT NULL,    -- 商品类型
    brand_name  VARCHAR(40)  NOT NULL,  -- 商品品牌
    goods_price DECIMAL(15,3) UNSIGNED NOT NULL DEFAULT 0, -- 商品价格
    is_show     BOOLEAN NOT NULL DEFAULT 1,    -- 是否上架
    is_saleoff  BOOLEAN NOT NULL DEFAULT 0    -- 是否打折
  );

 -- 写入记录

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('R510VC 15.6英寸笔记本','笔记本','华硕','3399',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Y400N 14.0英寸笔记本电脑','笔记本','联想','4899',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('G150TH 15.6英寸游戏本','游戏本','雷神','8499',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X550CC 15.6英寸笔记本','笔记本','华硕','2799',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X240(20ALA0EYCD) 12.5英寸超极本','超级本','联想','4999',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('U330P 13.3英寸超极本','超级本','联想','4299',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('SVP13226SCB 13.3英寸触控超极本','超级本','索尼','7999',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iPad mini MD531CH/A 7.9英寸平板电脑','平板电脑','苹果','1998',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iPad Air MD788CH/A 9.7英寸平板电脑 （16G WiFi版）','平板电脑','苹果','3388',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' iPad mini ME279CH/A 配备 Retina 显示屏 7.9英寸平板电脑 （16G WiFi版）','平板电脑','苹果','2788',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('IdeaCentre C340 20英寸一体电脑 ','台式机','联想','3499',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Vostro 3800-R1206 台式电脑','台式机','戴尔','2899',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iMac ME086CH/A 21.5英寸一体电脑','台式机','苹果','9188',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('AT7-7414LP 台式电脑 （i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux ）','台式机','宏碁','3699',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Z220SFF F4F06PA工作站','服务器/工作站','惠普','4288',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('PowerEdge T110 II服务器','服务器/工作站','戴尔','5388',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Mac Pro MD878CH/A 专业级台式电脑','服务器/工作站','苹果','28888',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W 头戴显示设备','笔记本配件','索尼','6999',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商务双肩背包','笔记本配件','索尼','99',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X3250 M4机架式服务器 2583i14','服务器/工作站','IBM','6888',DEFAULT,DEFAULT);
 
 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('玄龙精英版 笔记本散热器','笔记本配件','九州风神','',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W 头戴显示设备','笔记本配件','索尼','6999',DEFAULT,DEFAULT);

 INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商务双肩背包','笔记本配件','索尼','99',DEFAULT,DEFAULT);

创建表和数据

2. 求所有电脑产品的平均价格,并且保留两位小数，AVG,MAX,MIN,COUNT,SUM为聚合函数

SELECT ROUND(AVG(goods_price),2) AS avg_price FROM tdb_goods;

3.查询所有价格大于平均价格的商品，并且按价格降序排序

SELECT goods_id,goods_name,goods_price FROM tdb_goods 

    WHERE goods_price > (SELECT ROUND(AVG(goods_price),2) AS avg_price FROM tdb_goods) 

ORDER BY goods_price DESC;

4.查询类型为“超记本”的商品价格　

 SELECT goods_price FROM tdb_goods WHERE goods_cate = '超级本';

5.查询价格等于"超级本"价格的商品，并且按价格降序排列　　

 SELECT goods_id,goods_name,goods_price FROM tdb_goods 

   WHERE goods_price IN (SELECT goods_price FROM tdb_goods WHERE goods_cate = '超级本')

 ORDER BY goods_price DESC;

6.创建“商品类别”表

CREATE TABLE IF NOT EXISTS tdb_goods_cates(

    cate_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
    
    cate_name VARCHAR(40)

  );

7.查询tdb_goods表的类别记录，并且按"类别"分组

 SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;

8.将分组结果写入到tdb_goods_cates数据表　　

INSERT tdb_goods_cates (cate_name) SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;

9.通过tdb_goods_cates数据表来更新tdb_goods表中的'类别字段'

-- 1.通过内连接得到两个表的结果
select * from tdb_goods INNER JOIN tdb_goods_cates ON goods_cate = cate_name;

-- 2.通过上面的得到的临时表进行 类别字段更新
UPDATE tdb_goods INNER JOIN tdb_goods_cates ON goods_cate = cate_name
 
 SET goods_cate = cate_id;

10.通过CREATE...SELECT来创建[品牌]表并且同时写入记录

-- 1.获得品牌名称
SELECT brand_name FROM tdb_goods GROUP BY brand_name;

-- 2.创建品牌表,并且插入品牌数据
  CREATE TABLE tdb_goods_brands (

    brand_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,

    brand_name VARCHAR(40) NOT NULL

  ) SELECT brand_name FROM tdb_goods GROUP BY brand_name;

11.通过tdb_goods_brands 品牌表来更新 tdb_goods商品表

-- 错误
UPDATE tdb_goods  INNER JOIN tdb_goods_brands ON brand_name = brand_name

SET brand_name = brand_id;

-- Column 'brand_name' in field list is ambigous

-- 正确
UPDATE tdb_goods AS  g  INNER JOIN tdb_goods_brands AS b ON g.brand_name = b.brand_name

SET g.brand_name = b.brand_id;

12.查看tdb_goods的数据表结构　

DESC tdb_goods;

13.通过ALTER TABLE语句修改商品表结构,goods_cate更新为cate_id, brand_name更新为brand_id

ALTER TABLE tdb_goods  

CHANGE goods_cate cate_id SMALLINT NOT NULL,

CHANGE brand_name brand_id SMALLINT NOT NULL;

14.分别在tdb_goods_cates(类别表)和tdb_goods_brands(品牌表)插入记录

 INSERT tdb_goods_cates(cate_name) VALUES('路由器'),('交换机'),('网卡');

 INSERT tdb_goods_brands(brand_name) VALUES('海尔'),('清华同方'),('神舟');

15.在tdb_goods数据表写入任意记录

 INSERT tdb_goods(goods_name,cate_id,brand_id,goods_price) VALUES('LaserJet Pro P1606dn 黑白激光打印机','12','4','1849');

16.查询所有商品的详细信息(通过内连接实现)

SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g

   INNER JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id

   INNER JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id;

17.查询所有商品的详细信息(通过左外连接实现)　

SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g

   LEFT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id

   LEFT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id;

18.查询所有商品的详细信息(通过右外连接实现)

 SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g

   RIGHT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id

   RIGHT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id;

19.无限分类的数据表设计

   CREATE TABLE tdb_goods_types(
     type_id   SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
     type_name VARCHAR(20) NOT NULL,
     parent_id SMALLINT UNSIGNED NOT NULL DEFAULT 0
  ); 

  INSERT tdb_goods_types(type_name,parent_id) VALUES('家用电器',DEFAULT);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑、办公',DEFAULT);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('大家电',1);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('生活电器',1);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('平板电视',3);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('空调',3);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('电风扇',4);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('饮水机',4);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑整机',2);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑配件',2);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('笔记本',9);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('超级本',9);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('游戏本',9);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('CPU',10);
  INSERT tdb_goods_types(type_name,parent_id) VALUES('主机',10);

20.查找所有分类及其父类(将自身作为临时表使用)

select * FROM tdb_goods_types p1;
select * FROM tdb_goods_types p2;

SELECT p1.type_id,p1.type_name,p2.type_name as '父类'
	FROM tdb_goods_types p1 LEFT JOIN tdb_goods_types p2 
on p1.parent_id = p2.type_id

21. 复制编号为12,20的两条记录

  SELECT * FROM tdb_goods WHERE goods_id IN (19,20);

-- INSERT ... SELECT实现复制

  INSERT tdb_goods(goods_name,cate_id,brand_id) SELECT goods_name,cate_id,brand_id FROM tdb_goods WHERE goods_id IN (19,20);

22.查找重复记录

 SELECT goods_id,goods_name FROM tdb_goods 
    GROUP BY goods_name HAVING count(goods_name) >= 2;

23. 删除重复记录

#方式一:
  1.查询重复记录,获得重复字段
　　SELECT goods_name FROM tdb_goods ROUP BY goods_name HAVING count(goods_name) >= 2
  
  2.通过重复字段进行删除
	-- 错误
	DELETE FROM tdb_goods WHERE goods_name in(SELECT goods_name FROM tdb_goods 
    GROUP BY goods_name HAVING count(goods_name) >= 2)
	
	-- [Err] 1093 - You can't specify target table 'tdb_goods' for update in FROM clause
	-- 不能在同一个表中即查询数据又删除数据

    -- 正确
	DELETE FROM tdb_goods WHERE goods_name in(SELECT * from (SELECT goods_name FROM tdb_goods 
		GROUP BY goods_name HAVING count(goods_name) >= 2)as 别名)
	注意: 使用临时表 将子查询包裹,并起个别名

#方式二:保留一条
	DELETE FROM tdb_goods WHERE goods_name in(SELECT * from (SELECT goods_name FROM tdb_goods 
		GROUP BY goods_name HAVING count(goods_name) >= 2)as ss)
	and goods_id not in(SELECT * from (SELECT goods_id FROM tdb_goods 
		GROUP BY goods_name HAVING count(goods_name) >= 2)as 别名)

posted @ 2017-12-04 17:34 A.隔壁老王阅读(807) 评论(0) 编辑收藏举报

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MySQL 练习题3

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