MySQL数据类型及表操作

Posted 2022-10-21

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建立简单表

use wxdb;
create table  wx_student(
    id int ,
    name varchar(30)
);
select database();
show tables;
select * from wx_student;

use wxdb;
create table t1(t int);
create table t2(t int);
create table t3(t int);
create table t4(t int);
create table t5(t int);

作业：

建立数据库hbcf

建立一个表cf_news

show create table cf_news;
create table `cf_news` (
  `id` varchar(36) not null,
  `subject` varchar(200) default null,
  `content` longtext,
  `category` varchar(20) default null,
  `logoUrl` varchar(300) default null,
  `times` int default 0,
  `adddate` datetime default null,
  `ispublish` tinyint default 0 comment 0未发布 1已发布,
  `publishdate` datetime default null,
  `isdel` tinyint default 0 comment 0未删除 1删除 ,
  primary key (`id`) comment 注释
) engine=innodb default charset=utf8

删除表

-- 删除表
drop table wx_student;
drop table if exists wx_student;
-- 批量删除表
drop table if exists t1,t2,t3,t4,t5;

修改表及列及数据类型

-- 修改表名  student  cf_student  cf_user cf_admin cf_car
rename table w_student to cf_student;
alter table cf_student rename st;

-- 查看表结构
describe st;
desc st;
-- 查看建立表语句
show create table st;
CREATE TABLE `st` (
   `id` int unsigned NOT NULL AUTO_INCREMENT,
   `name` varchar(30) NOT NULL,
   `gender` enum(男,女) DEFAULT NULL,
   `course` set(计算机英语,高数,离散数学,线性代数) DEFAULT NULL,
   PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8mb3

-- 增加一列（字段）
-- 删除一列（字段）
-- 修改列名
-- 修改列的数据类型 int bigint varchar int  varchar(30)  varchar(5)
select * from st;

-- 增加一列
alter table st add address varchar(255) not null default 郑州市;
alter table st add age tinyint unsigned not null default 18 first; 
alter table st add age tinyint unsigned default 0 after name;

-- 删除一列
alter table st drop address;
alter table st drop column age;

-- 修改列名 name StudentName  sname
alter table st rename column name to sname;
alter table st change sname name varchar(30) first;
alter table st change name name varchar(30) after id;

-- 修改列的数据类型及精度
alter table st modify name varchar(100) after address;
alter table st modify name varchar(50) after id;

-- 复制表的结构
-- create table t6(t int);
create table st2 like st;

show create table st2;
select * from st2;

-- 插入数据
insert into st2 select * from st;

show tables;
-- 根据查询的结构，建立一个没有相关约束的表,可以直接插入数据
create table st3 as select id,name from st;
create table st4 as select id,name,address from st where name like 李%;
select * from st3;
show create table st3;
drop table st3;

select * from st4;

表相关的约束(PK-FK)

主键约束 PK

-- 表的相关约束
-- 1. PK  primary key 一个表只有一个主键约束，
create table t1(
    id int unsigned auto_increment primary key,
    name varchar(30)
);

create table t2(
   id int unsigned auto_increment,
   name varchar(30),
   primary key(id)
);

create table t3(
   id int,
   name varchar(30)
);
alter table t3 add primary key(id);
show create table t3;

create table t4(
   id char(36),
   name varchar(30),
   primary key(id)
);
insert into t4 value(uuid(),jack);
insert into t4 values(uuid(),jack),(uuid(),李四),(uuid(),james);
select * from t4;




show create table mysql.user;

唯一约束 unique

-- 表的相关约束
-- 建立唯一约束
create table t(
    id int unsigned auto_increment,
    name varchar(15) unique , /* 此字段，值不能重复，但可以null重复*/
    age tinyint unsigned default 18,
    primary key(id)
)

insert into t(name) values(lisi),(jack),(null),(null),(null);
insert into t values(null,aaa,29),(null,fff,29);

select * from t;

truncate t;

默认值 default 18

create table w_student(
    id char(36) ,
    name varchar(30) not null,
    gender enum(男,女) default 男,
    age tinyint unsigned default 18,
    birthday date  default 1000-01-01,
    regtime datetime default now(),
    updatetime timestamp default current_timestamp on update current_timestamp,
    primary key(id)
);

非空 not null 不写 default null

外键约束 FK

-- 表的相关约束
-- 外键约束 foreign key
show tables;
drop table t,w_student;
-- 建立老师表
create table teacher(
    id int unsigned auto_increment,
    name varchar(30),
    primary key(id)
);
insert into teacher values(null,李老师),(null,周老师),(null,郑老师),(null,刘老师);
select * from teacher;
delete from teacher where id = 3;

-- 建立学生表，学生表的teacher_id 建立一个外键，关联到teacher(id)
create table student(
    id int unsigned auto_increment,
    name varchar(30),
    teacher_id int unsigned,
    primary key(id),
    constraint stfk foreign key(teacher_id) references teacher(id)
);
insert into student (name) values(张三),(李四);

drop table teacher;

select * from student;

show engines;
show tables;
   select *
   from teacher;

   delete
   from teacher
   where id = 1;

   select *
   from student;

   drop table student,teacher;

   -- 删除外键
   alter table student
       drop constraint stfk;

   -- 删除一列
   alter table student
       drop teacher_id;
   alter table student
       add tid int unsigned;

   create table teacher
   (
       id   int unsigned,
       name varchar(30),
       primary key (id)
   );
   create table student
   (
       id   int unsigned,
       name varchar(30),
       tid  int unsigned,
       primary key (id)
   );

   -- 建立外键
   alter table student
       add constraint stfk foreign key (tid) references teacher (id);

   -- 建立外键，如果主表删除，自动设置关联表设置null,如果主表修改，自动设置关联表更新
   alter table student
       add constraint stfk foreign key (tid) references teacher (id)
           on delete set null on update cascade;

   insert into teacher
   values (1, 李老师),
          (3, 赵老师);

   insert into student
   values (6, 李四, 1);

   select *   from student;
   select *   from teacher;
   delete   from teacher   where id = 1;

   update student   set tid = 3   where id = 6;

   update teacher   set id = 110   where id = 3;

数据类型

数字类型int decimal

Type	Storage (Bytes)	Minimum Value Signed	Maximum Value Signed	Maximum Value Unsigned
TINYINT	1	-128	127	255
SMALLINT	2	-32768	32767	65535
MEDIUMINT	3	-8388608	8388607	16777215
INT	4	-2147483648	2147483647	4294967295
BIGINT	8	-263	263-1	264-1

型	大小	范围（有符号）	范围（无符号）	用途
TINYINT	1 byte	(-128，127)	(0，255)	小整数值
SMALLINT	2 bytes	(-32 768，32 767)	(0，65 535)	大整数值
MEDIUMINT	3 bytes	(-8 388 608，8 388 607)	(0，16 777 215)	大整数值
INT或INTEGER	4 bytes	(-2 147 483 648，2 147 483 647)	(0，4 294 967 295)	大整数值
BIGINT	8 bytes	(-9,223,372,036,854,775,808，9 223 372 036 854 775 807)	(0，18 446 744 073 709 551 615)	极大整数值
FLOAT	4 bytes	(-3.402 823 466 E+38，-1.175 494 351 E-38)，0，(1.175 494 351 E-38，3.402 823 466 351 E+38)	0，(1.175 494 351 E-38，3.402 823 466 E+38)	单精度浮点数值
DOUBLE	8 bytes	(-1.797 693 134 862 315 7 E+308，-2.225 073 858 507 201 4 E-308)，0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308)	0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308)	双精度浮点数值
DECIMAL	对DECIMAL(M,D) ，如果M>D，为M+2否则为D+2	依赖于M和D的值	依赖于M和D的值	小数值

--  ZEROFILL UNSIGNED
-- BIT[(M)] 1-64
-- TINYINT[(M)] [UNSIGNED] [ZEROFILL]  -128 - 127  0-255
SMALLINT[(M)] [UNSIGNED] [ZEROFILL]
A small integer. The signed range is -32768 to 32767. 
The unsigned range is 0 to 65535.
   
MEDIUMINT[(M)] [UNSIGNED] [ZEROFILL]
   A medium-sized integer. The signed range is -8388608 to 8388607. 
   The unsigned range is 0 to   16777215.

INT[(M)] [UNSIGNED] [ZEROFILL]
   A normal-size integer. The signed range is -2147483648 to 2147483647. 
   The unsigned range is 0   to 4294967295.

INTEGER[(M)] [UNSIGNED] [ZEROFILL]
   This type is a synonym for INT.

BIGINT[(M)] [UNSIGNED] [ZEROFILL]
   A large integer. The signed range is -9223372036854775808 to 9223372036854775807. The
   unsigned range is 0 to 18446744073709551615.
   
   -- 整数类型  bit tinyint smallint mediumint int integer bigint 8byte
   -- 小数 decimal(p,s)  numeric(p,s) float  double
   -- cf_student
   create table cf_student(
       id int(3) zerofill unsigned auto_increment,
       name varchar(30) not null,
       age tinyint unsigned default 18,
       money decimal(10,2) comment 金额,  
       primary key(id)
   )engine=innodb default charset=utf8 auto_increment=202101;
   drop table cf_student;
   
   insert into cf_student values(null,andy,38,9);
   insert cf_student(name) values(李四),(王五),(赵六七);
   
   select * from cf_student;

字符字符串char varchar

Value	CHAR(4)	Storage Required	VARCHAR(4)	Storage Required
		4 bytes		1 byte
ab	ab	4 bytes	ab	3 bytes
abcd	abcd	4 bytes	abcd	5 bytes
abcdefgh	abcd	4 bytes	abcd	5 bytes

类型	大小	用途
CHAR	0-255 bytes	定长字符串
VARCHAR	0-65535 bytes	变长字符串varchar(21835)
TINYBLOB	0-255 bytes	不超过 255 个字符的二进制字节
TINYTEXT	0-255 bytes	短文本字符串
BLOB文件	0-65 535 bytes	二进制形式的长文本数据
TEXT	0-65 535 bytes	长文本数据
MEDIUMBLOB文件	0-16 777 215 bytes	二进制形式的中等长度文本数据
MEDIUMTEXT	0-16 777 215 bytes	中等长度文本数据
LONGBLOB文件	0-4 294 967 295 bytes	二进制形式的极大文本数据 4G 文件字节
LONGTEXT	0-4 294 967 295 bytes	极大文本数据 4GB

日期时间date datetime

Data Type	Storage Required Before MySQL 5.6.4	Storage Required as of MySQL 5.6.4
YEAR	1 byte	1 byte
DATE	3 bytes	3 bytes
TIME	3 bytes	3 bytes + fractional seconds storage
DATETIME	8 bytes	5 bytes + fractional seconds storage
TIMESTAMP	4 bytes	4 bytes + fractional seconds storage

Data Type	“Zero” Value
DATE	0000-00-00 java.util.time.LocalDate
TIME	00:00:00 java.util.time.LocalTime
DATETIME	0000-00-00 00:00:00 java.util.Date
TIMESTAMP	0000-00-00 00:00:00
YEAR	0000

类型	大小 ( bytes)	范围	格式	用途
DATE	3	1000-01-01/9999-12-31	YYYY-MM-DD	日期值
TIME	3	-838:59:59/838:59:59	HH:MM:SS	时间值或持续时间
YEAR	1	1901/2155	YYYY	年份值
DATETIME	8	1000-01-01 00:00:00/9999-12-31 23:59:59	YYYY-MM-DD HH:MM:SS	混合日期和时间值
TIMESTAMP	4	1970-01-01 00:00:00/2038结束时间是第 2147483647 秒，北京时间 2038-1-19 11:14:07，格林尼治时间 2038年1月19日凌晨 03:14:07	YYYYMMDD HHMMSS	混合日期和时间值，时间戳

-- 建立表
create table w_student(
    id int unsigned auto_increment comment 学号,
    name varchar(30) not null,
    gender enum(男,女),
    birthday date,
    regtime datetime default now(),
    updatetime timestamp DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP comment 每次数据都会自动更新当前时间,
    primary key(id)
);

show tables;
create table t(t int);
insert into w_student(name,birthday) values(李四,2002-09-20);
select * from w_student;

update w_student set name = 李强2 where 0;

布尔BOOL, BOOLEAN

-- bool boolean tinyint(1) 0-255  bit tinyint

create table t2(
    isA bit,
    isB bool,
    isC boolean,
    isD tinyint(1) unsigned,
    ns varchar(30)
)

-- show create table t2;
create table `t2` (
  `isA` bit(1) default null,
  `isB` tinyint(1) default null,
  `isC` tinyint(1) default null,
  `isD` tinyint unsigned default null,
  `ns` varchar(30) default null
) engine=innodb default charset=utf8mb3

create table t3(t bit);
insert into t3 values(1),(0)

select * from t3;


select * from t2;

insert t2 values(true,true,false,false,jack);

insert t2 values(false,false,false,false,jack);
select * from t2 where not isC;


-- 0 false 非0就是true
select * from t2 where  null is null;

复合类型set enum

-- 学习 set 集合  enum 枚举
select database();
create table wxdb.t1(t int);
use wxdb;
show tables;
drop table if exists t,t1,t2,t3,w_student;
/* 在wxdb 数据库建立表w_studdnet */
create table w_student(
   id int unsigned auto_increment primary key,
   name varchar(30) not null,
   gender enum(男,女),
   course set(计算机英语,高数,离散数学,线性代数) not null
);

select * from w_student;
insert into w_student(name) values(李四),(jack);
insert into w_student value(null,lisi,女,线性代数,高数,离散数学,计算机英语);

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