first-commit

数据库MySQL/数据库基础.sql

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+show databases;
+
+drop database user_info;
+
+create database if not exists nengdie;
+
+use nengdie;
+
+show create database nengdie;
+
+drop table if exists user_info;
+
+create table user_info (
+    user_id smallint(5) primary key auto_increment,
+    age tinyint(3) not null,
+    gender varchar(10) default 'male',
+    email varchar(20),
+    phone_number varchar(20) unicode
+);
+
+describe user_info;
+show create table user_info;
+
+# modify column data format
+alter table user_info modify phone_number varchar(25);
+
+alter table user_info change gender gender varchar(8) default 'male' after phone_number;
+
+alter table user_info rename user_info1;
+show tables;
+drop table user_info1;
+
+alter table user_info add user_name varchar(30) after user_id;
+
+describe user_info;
+
+# DML
+insert into user_info (age, user_name,gender, email, phone_number)
+values
+       (20,'wdd','male','wdd@qq.cm','123456'),
+       (18,'cxc','male','cxc@163.com','13911'),
+       (12,'die','male','die@qq.com','234325');
+
+select * from user_info;
+
+delete from user_info where user_id=3;
+
+insert into user_info (age, user_name,gender, email, phone_number)
+values
+       (12,'die','male','die@qq.com','234325'),
+       (18,'fangfang','female','fang@qq.com','123');
+
+update user_info set user_name='fang' where user_id=5;
+
+
+#DQL
+select user_id,user_name from user_info;
+
+select user_name,email from user_info where user_id=4;
+
+select user_id,email from user_info where user_info.user_name like '%c';
+
+update user_info set phone_number=null where user_id=5;
+select * from user_info;
+
+select user_name,age,gender from user_info where phone_number is null ;
+
+select user_name, email from user_info where age=18 and user_info.gender='male';
+
+select gender,count(*) as count_num from user_info group by gender;
+
+# DQL high level
+## union
+
+select * from user_info where user_info.gender='female'
+union
+select * from user_info where user_info.user_name like '%c';
+
+drop table if exists fav_thing;
+create table fav_thing (
+    fav_id tinyint(4) primary key auto_increment,
+    fav_thing varchar(150),
+    fav_user_id smallint(5) not null,
+    constraint fk_fav_user foreign key fav_thing(fav_user_id) references user_info(user_id)
+);
+
+describe fav_thing;
+
+insert into fav_thing (fav_thing, fav_user_id)
+VALUES
+       ('reading',1),
+       ('fighting',5);
+
+select * from fav_thing;
+
+## inner join
+select * from user_info
+inner join
+    fav_thing ft on user_info.user_id = ft.fav_user_id;
+
+select * from user_info
+inner join fav_thing;
+
+select * from fav_thing
+inner join user_info;
+
+## left outer join
+## 查询所有的user对应的fav_thing
+select * from user_info
+left join
+    fav_thing ft on user_info.user_id = ft.fav_user_id;
+
+select * from fav_thing
+left join user_info ui on ui.user_id = fav_thing.fav_user_id;
+
+select * from user_info
+cross join
+    fav_thing ft on user_info.user_id = ft.fav_user_id;
+
+select * from fav_thing
+cross join user_info ui on ui.user_id = fav_thing.fav_user_id;
+
+## full outer join
+select * from user_info
+full join fav_thing ft on full.user_id = ft.fav_user_id;
+
+select * from fav_thing
+full join user_info ui on ui.user_id = full.fav_user_id;
+