学点儿数据库_Day12_数据库SQL练习题

0 版本与工具

mysql-8.0.31
Navicat Premium 16
每做一题，选中相应代码运行即可，很方便
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1 建表

create table goods (
  goods_id mediumint(8) unsigned primary key auto_increment,
  goods_name varchar(120) not null default '',
  cat_id smallint(5) unsigned not null default '0',
  brand_id smallint(5) unsigned not null default '0',
  goods_sn char(15) not null default '',
  goods_number smallint(5) unsigned not null default '0',
  shop_price decimal(10,2) unsigned not null default '0.00',
  market_price decimal(10,2) unsigned not null default '0.00',
  click_count int(10) unsigned not null default '0'
) ;

insert into `goods` values (1,'kd876',4,8,'ecs000000',1,1388.00,1665.60,9),
(4,'诺基亚n85原装充电器',8,1,'ecs000004',17,58.00,69.60,0),
(3,'诺基亚原装5800耳机',8,1,'ecs000002',24,68.00,81.60,3),
(5,'索爱原装m2卡读卡器',11,7,'ecs000005',8,20.00,24.00,3),
(6,'胜创kingmax内存卡',11,0,'ecs000006',15,42.00,50.40,0),  
(7,'诺基亚n85原装立体声耳机hs-82',8,1,'ecs000007',20,100.00,120.00,0),
(8,'飞利浦9@9v',3,4,'ecs000008',1,399.00,478.79,10),
(9,'诺基亚e66',3,1,'ecs000009',4,2298.00,2757.60,20),
(10,'索爱c702c',3,7,'ecs000010',7,1328.00,1593.60,11),
(11,'索爱c702c',3,7,'ecs000011',1,1300.00,0.00,0),
(12,'摩托罗拉a810',3,2,'ecs000012',8,983.00,1179.60,13),
(13,'诺基亚5320 xpressmusic',3,1,'ecs000013',8,1311.00,1573.20,13),
(14,'诺基亚5800xm',4,1,'ecs000014',1,2625.00,3150.00,6),
(15,'摩托罗拉a810',3,2,'ecs000015',3,788.00,945.60,8),
(16,'恒基伟业g101',2,11,'ecs000016',0,823.33,988.00,3),
(17,'夏新n7',3,5,'ecs000017',1,2300.00,2760.00,2),
(18,'夏新t5',4,5,'ecs000018',1,2878.00,3453.60,0),
(19,'三星sgh-f258',3,6,'ecs000019',12,858.00,1029.60,7),
(20,'三星bc01',3,6,'ecs000020',12,280.00,336.00,14),
(21,'金立 a30',3,10,'ecs000021',40,2000.00,2400.00,4),
(22,'多普达touch hd',3,3,'ecs000022',1,5999.00,7198.80,16),
(23,'诺基亚n96',5,1,'ecs000023',8,3700.00,4440.00,17),
(24,'p806',3,9,'ecs000024',100,2000.00,2400.00,35),
(25,'小灵通/固话50元充值卡',13,0,'ecs000025',2,48.00,57.59,0),
(26,'小灵通/固话20元充值卡',13,0,'ecs000026',2,19.00,22.80,0),
(27,'联通100元充值卡',15,0,'ecs000027',2,95.00,100.00,0),
(28,'联通50元充值卡',15,0,'ecs000028',0,45.00,50.00,0),
(29,'移动100元充值卡',14,0,'ecs000029',0,90.00,0.00,0),
(30,'移动20元充值卡',14,0,'ecs000030',9,18.00,21.00,1),
(31,'摩托罗拉e8 ',3,2,'ecs000031',1,1337.00,1604.39,5),  
(32,'诺基亚n85',3,1,'ecs000032',4,3010.00,3612.00,9);

-- 分类表
create table category (
    cat_id smallint unsigned auto_increment primary key,
    cat_name varchar(90) not null default '',
    parent_id smallint unsigned
);

INSERT INTO `category` VALUES
(1,'手机类型',0),
(2,'CDMA手机',1),
(3,'GSM手机',1),
(4,'3G手机',1),
(5,'双模手机',1),
(6,'手机配件',0),
(7,'充电器',6),
(8,'耳机',6),
(9,'电池',6),
(11,'读卡器和内存卡',6),   
(12,'充值卡',0),
(13,'小灵通/固话充值卡',12),
(14,'移动手机充值卡',12),
(15,'联通手机充值卡',12);

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2 练习与答案

2.0 知识点

无限级分类(上树)：
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select where常用运算符:
NOT可以否定IN、BETWEEN、EXISTS

2.1 条件查询1

DESC goods;

-- 1:主键为32的商品
SELECT * FROM goods
WHERE goods_id=32;
-- 2:不属第3栏目的所有商品（category中id为3）
SELECT * FROM goods
WHERE cat_id!=3;
-- 3:本店价格高于3000元的商品
SELECT * FROM goods
WHERE market_price>3000;
-- 4:本店价格低于或等于100元的商品
SELECT * FROM goods
WHERE market_price<=100;
-- 5:取出第4栏目或第11栏目的商品
SELECT * FROM goods
WHERE cat_id=4 OR cat_id=11;
-- 
SELECT * FROM goods
WHERE cat_id IN (4,11);
-- 6:取出100<=价格<=500的商品
SELECT * FROM goods
WHERE market_price BETWEEN 100 AND 500;
-- BETWEEN AND是能取到开始和结束的值，等价于>= and <=

-- 7:取出不属于第3栏目且不属于第11栏目的商品(and,或not in分别实现)
SELECT * FROM goods
WHERE cat_id!=3 AND cat_id!=11;

SELECT * FROM goods
WHERE cat_id NOT IN (3,11);

2.2 条件查询2

-- 8:取出价格大于100且小于300,或者大于4000且小于5000的商品()
-- 要适当的加括号(括号的优先级比AND和OR优先级高)，不加括号数据也正确，只是巧合，因为AND优先级要高于OR优先级，写出有歧义的语句并不能显出你多厉害
-- 任何时候使用AND和OR操作符时候，都应该加括号明确的分组操作符，不要过分依赖默认求值顺序，及时它确实如你希望的那样。使用括号没有什么坏处，它能消除歧义。
-- select * from goods where () OR ();
SELECT * FROM goods
WHERE (market_price>100 AND market_price<300) OR (market_price>4000 AND market_price<5000);
-- 9:取出第3个栏目下面价格<1000或>3000,并且点击量>5的系列商品
SELECT * FROM goods
WHERE (cat_id=3) AND (market_price<1000 OR market_price>3000) AND (click_count>5);

2.3 子查询

-- 10:取出第1个栏目下面的商品(注意:1栏目下面没商品,但其子栏目下有)
SELECT * FROM category
WHERE cat_id = 1 OR parent_id=1;
SELECT * FROM goods
WHERE cat_id IN (SELECT cat_id FROM category WHERE cat_id=1 OR parent_id=1);-- 子查询

2.4 模糊查询

-- 11:取出名字以"诺基亚"开头的商品
-- like 模糊匹配
-- % 通配任意字符
-- _ 通配单一字符
SELECT * FROM goods
WHERE goods_name LIKE '诺基亚%';
-- 12:取出名字为"诺基亚nxx"的手机
SELECT * FROM goods
WHERE goods_name LIKE '诺基亚n__';
-- 13:取出名字不以"诺基亚"开头的商品
SELECT * FROM goods
WHERE goods_name NOT LIKE '诺基亚%';
-- 14:取出第3个栏目下面价格在<1000或者>3000,并且点击量>5 "诺基亚"开头的系列商品
SELECT * FROM goods
WHERE (cat_id=3) 
AND (market_price<1000 OR market_price>3000) 
AND (click_count>5) 
AND (goods_name LIKE '诺基亚%');

2.5 数据库字符串操作

//java
public static void main(String[] args) {
        String goodsName = "诺基亚原装5800耳机";
        String name = "HTC" + goodsName.substring(3);
        System.out.println(name);//HTC原装5800耳机
    }

-- 15:把goods表中商品名为'诺基亚xxxx'的商品,改为'HTCxxxx',
-- 提示:大胆的把列看成变量,参与运算,甚至调用函数来处理 .
-- substr(),concat(),trim(),ltrim(),rtrim()
-- 修改
UPDATE goods SET goods_name = CONCAT('HTC',TRIM(leading '诺基亚' FROM goods_name))
WHERE goods_name LIKE '诺基亚%';
-- 修改后再查询
UPDATE goods SET goods_name = CONCAT('HTC',SUBSTR(goods_name,4)) AS goods_name
WHERE goods_name LIKE '诺基亚%';

SELECT goods_id,goods_name FROM goods 
WHERE goods_name LIKE 'HTC%';

-- 查询 ----
SELECT goods_id,SUBSTR(goods_name, 4) FROM goods 
WHERE goods_name LIKE '诺基亚%';
-- 查询并拼接 ----
SELECT goods_id,CONCAT('HTC',SUBSTR(goods_name,4)) FROM goods 
WHERE goods_name LIKE '诺基亚%';

2.6 聚合查询(聚合函数)

-- 15:计算指定分类(cat_id=3)下面商品的平均价格，计算平均价格时候去掉重复价格的
-- 只包含不同的值，指定DISTINCT参数 (去重)
SELECT DISTINCT market_price 
FROM goods
WHERE cat_id=3;

SELECT market_price 
FROM goods
WHERE cat_id=3;

SELECT AVG(market_price) AS '平均价格' 
FROM goods
WHERE cat_id=3;

SELECT AVG(DISTINCT market_price) AS '平均价格' 
FROM goods
WHERE cat_id=3;

-- 16:组合聚集函数，SELECT可以根据需要包含多个聚集函数
-- goods_count price_min  price_max price_avg

SELECT COUNT(*) AS 'goods_count',
	MIN(market_price) AS 'price_min',
	MAX(market_price) AS 'price_max',
	AVG(market_price) AS 'price_avg'
FROM goods;

2.7 order by 与 limit

-- order by 与 limit：
-- LIMIT 子句可以被用于强制 SELECT 语句返回指定的记录数。
-- LIMIT 接受一个或两个数字参数。参数必须是一个整数常量。
-- 如果给定两个参数，第一个参数指定第一个返回记录行的偏移量，第二个参数指定返回记录行的最大数目。初始记录行的偏移量是 0(而不是 1)
SELECT * FROM goods LIMIT 0,3;
SELECT * FROM goods;
-- 1、按照栏目由低到高排序，栏目内部按照价格由高到低排序
SELECT * 
FROM goods
ORDER BY cat_id ASC,market_price DESC;
-- 2、取出价格最高的前三名商品
-- limit offset,rowcount
-- limit 偏移到哪个位置,往下数几个
SELECT * 
FROM goods
ORDER BY market_price DESC
LIMIT 0,3;
-- 3、取出点击量第三名到第五名的商品
SELECT * 
FROM goods
ORDER BY click_count DESC
LIMIT 2,3;

2.8 order by 与 having

-- 1、这个店积压的货款：
SELECT goods_id,goods_name,cat_id,goods_number*shop_price AS '货款' FROM goods;
SELECT SUM(goods_number*shop_price) '总货款' FROM goods;
-- 2、查询该店每个栏目下挤压的货款
SELECT cat_id,SUM(goods_number*shop_price) AS total_price FROM goods
GROUP BY cat_id;
-- 3、查询该店每个栏目下挤压的货款 > 100
SELECT cat_id,total_price FROM 
(SELECT cat_id,SUM(goods_number*shop_price) AS total_price FROM goods GROUP BY cat_id) AS table2
WHERE total_price>100
ORDER BY total_price,cat_id;
-- 3、查询该店每个栏目下挤压的货款 > 100
SELECT cat_id,SUM(goods_number*shop_price) AS total_price
FROM goods GROUP BY cat_id HAVING total_price>100
ORDER BY total_price,cat_id;

DROP TABLE goods;

备注：我们经常发现，用 GROUP BY 分组的数据确实是以分组顺序输出的。但并不总是这样，这不是 SQL 规范所要求的。此外，即使特定的 DBMS（DateBaseManagerSystem，数据库管理系统）总是按给出的 GROUP BY 子句排序数据，用户也可能会要求以不同的顺序排序。应该提供明确的 ORDER BY 子句，即使其效果等同于 GROUP BY 子句。