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+## 1.作业
+
+```sql
+CREATE DATABASE if not exists yuanshen charset utf8;
+USE yuanshen;
+
+CREATE TABLE if not exists roleinfo(
+roleId VARCHAR(5),
+roleName VARCHAR(4),
+roleSex VARCHAR(2),
+roleAge int(5),
+roleAddress VARCHAR(5),
+destinity VARCHAR(30)
+);
+
+insert into roleinfo VALUES
+(1,'甘雨','女',3000,'璃月','kylin'),
+(2,'魈','男',2000,'璃月','golden winged peng'),
+(3,'刻晴','女',26,'璃月','alioth'),
+(4,'凯亚','男',25,'蒙德','peacockfeather'),
+(5,'芭芭拉','女',17,'蒙德','goldencup'),
+(6,'八重神子','女',500,'稻妻','fairy fox')
+;
+
+CREATE TABLE if not exists draw(
+roleId int(2),
+roleName VARCHAR(4),
+drawRole int(3),
+drawWeapon int(3)
+);
+
+insert into draw VALUES
+(1,'甘雨',10,70),
+(2,'魈',50,60),
+(3,'刻晴',20,40),
+(4,'凯亚',50,80),
+(5,'芭芭拉',70,90),
+(6,'八重神子',40,30)
+;
+
+CREATE TABLE if not exists capacity(
+roleId int(2),
+roleName varchar(4),
+vitality int(5),
+denfensivePower int(5),
+attack int(5)
+);
+
+insert into capacity values
+(1,'甘雨',9797,630,335),
+(2,'魈',12736,799,349),
+(3,'刻晴',13103,799,323),
+(4,'凯亚',11636,792,233),
+(5,'芭芭拉',9787,669,160),
+(6,'八重神子',10372,569,340)
+;
+
+select * FROM roleinfo;
+select * FROM draw;
+select * FROM capacity;
+
+-- 1.查询角色信息表(roleinfo)中所有信息，给每列取上中文名称
+SELECT roleId as id,roleName as 姓名,roleSex as 性别,roleAddress as 来自,destinity as 命座 FROM roleinfo;
+-- 2.查询属性表(capacity)中的生命力，防御力，攻击力三列的信息
+SELECT vitality,denfensivePower,attack FROM capacity;
+-- 3.查询抽卡表(draw)中的角色名,抽角色,抽专武四列的信息,并为这三列取中文名字
+SELECT roleName as 甘雨,drawrole as 抽角色,drawweapon as 抽专武 FROM draw;
+-- 4.查询角色信息表(roleinfo)中角色来自哪几个地方
+SELECT DISTINCT roleAddress FROM roleinfo;
+-- 5.查询角色信息表(roleinfo)中前4行记录
+SELECT * FROM roleinfo limit 4;
+-- 6.查询角色信息表(roleinfo)中前3个角色的名称和命座
+SELECT roleName,destinity FROM roleinfo limit 3;
+-- 7.将地址是璃月，年龄是3000的角色的所有信息查询出来
+SELECT * FROM roleinfo WHERE roleAddress='璃月' and roleAge=3000;
+-- 8.将生命力在10000-12000之间的信息查询出来,并按照生命力升序排列
+SELECT * FROM capacity WHERE vitality BETWEEN 10000 AND 12000 ORDER BY vitality asc;
+-- 9.查询来自璃月或者稻妻的角色的所有信息
+SELECT * FROM roleinfo WHERE roleAddress='璃月' or roleAddress='稻妻';
+-- 10.查询出抽卡不在小保底(90)和大保底(180)之间的信息，并按照抽角色次数降序排列
+SELECT * FROM draw WHERE drawrole not between 90 and 180 order by drawrole desc;
+-- 11.查询角色地址中有'月'字的信息
+SELECT * FROM roleinfo WHERE roleAddress like '%月%';
+-- 12.显示攻击力最高的角色的id,姓名,抽角色次数,抽专武次数
+SELECT * FROM roleinfo WHERE attack=(SELECT max(attack)FROM capacity)
+-- 13.把角色信息表(roleinfo)和角色属性表(capacity)连接
+SELECT * from roleinfo JOIN capacity;
+-- 14.把角色信息表(roleinfo)和角色属性表(capacity)左外连接
+SELECT * from roleinfo left join capacity on roleinfo.roleId=capacity.roleId;
+-- 15.把角色信息表(roleinfo)和角色属性表(capacity)右外连接
+SELECT * from roleinfo RIGHT JOIN capacity on roleinfo.roleId=capacity.roleId;
+-- 16.把角色信息表(roleinfo)和角色属性表(capacity)内连接
+SELECT * from roleinfo INNER JOIN capacity on roleinfo.roleId=capacity.roleId;
+-- 17.把角色信息表(roleinfo)和角色属性表(capacity)取并集然后去交集
+select * from roleinfo left join capacity on roleinfo.roleId = capacity.roleId where capacity.roleId is null
+union
+select * from roleinfo right join capacity on roleinfo.roleId = capacity.roleId where roleinfo.roleId is null;
+-- 18.查询所有璃月角色和女角色的信息
+SELECT * from roleinfo where roleAddress='璃月' and roleSex='女';
+-- 19.查询和“魈”同性别的同学的所有信息
+SELECT * from roleinfo where roleSex(SELECT roleSex from roleinfo where roleName='魈');
+```
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diff --git "a/20 \347\237\263\350\211\257\346\266\233/\347\254\254\345\205\255\347\273\204\344\275\234\344\270\232.md" "b/20 \347\237\263\350\211\257\346\266\233/\347\254\254\345\205\255\347\273\204\344\275\234\344\270\232.md"
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+## 1.作业
+
+```sql
+CREATE DATABASE stu CHARSET utf8;
+USE stu;
+CREATE TABLE `user`(
+user_id INT,
+user_name VARCHAR(20),
+user_tel VARCHAR(20),
+ordertime DATE
+);
+CREATE TABLE `order`(
+`order_id` INT,
+user_id INT,
+type VARCHAR(20),
+food VARCHAR(20),
+number INT,
+price INT
+);
+
+INSERT INTO `user` VALUES
+(1,'张三','19865645691','2023-3-13'),
+(2,'李四','12345675691','2023-3-13'),
+(3,'王五','12895678901','2023-3-13'),
+(4,'老六','12345678691','2023-3-14'),
+(5,'小七','18945678031',NULL),
+(6,'老八','19345678561', '2023-3-16'),
+(7,'朱九','15845679911',NULL);
+
+INSERT INTO `order` VALUES
+ (1,1,'快餐','肯德基全家桶',1,50),
+ (2,1,'快餐','可乐' ,4 ,20),
+ (3,6,'饮料','柠檬水',2,16),
+ (4,2,'米饭','鱼香肉丝盖饭',5,60),
+ (5,2,'饮料','珍珠奶茶',3,22),
+ (6,3,'粉面类','螺蛳粉',4,28),
+ (7,4,'粉面类','凉拌面',1,10);
+--  1.在用户表（user）新增一个性别字段user_sex，数据类型为char。
+ALTER TABLE `user` ADD user_sex CHAR;
+-- 2.由于顾客3退单，请把此订单删除。
+DELETE FROM `order` WHERE user_id =3;
+-- 3.老八的电话号码换新了，请将他的号码更新为8888888888。
+UPDATE `user` set user_tel='8888888888'WHERE user_name = '老八';
+-- 4.查询order表里的最高金额和总金额。
+SELECT MAX(price) 最高金额,SUM(price) 总金额 FROM `order`;
+-- 5.查询每个顾客分别订购了几个类别。
+SELECT type,user_id,COUNT(user_id) FROM `order` GROUP BY type,user_id;
+-- 6.查询饮料的总金额
+SELECT SUM(price)总金额 FROM `order` WHERE type = '饮料';
+-- 7.查询订单表（order）里的订单号，类别（type），食物（food）.
+SELECT order_id 订单号,type 类别,food 食物 FROM `order`;
+-- 8.查询没吃饭的人的所有信息
+SELECT * FROM `user` WHERE user_id not IN (SELECT DISTINCT user_id FROM `order`);
+-- 9.查询姓老的人的全部信息及订单信息
+SELECT * FROM `user` WHERE user_name LIKE '老%';
+-- 10.查询总金额大于20的订单里最大值的用户信息，使用降序排列。
+SELECT * FROM `user` a LEFT JOIN `order` b ON 
+a.user_id =b.user_id 
+WHERE price *number in (SELECT max(price * number) FROM `order`) and price * number >20;
+```
+
+
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