//以管理员身份运行cmd
net start mysql80
net stop mysql80
“开始”找到MySQL
mysql [-h 127.0.0.1] [-P 3306] -u root -p
mysql -u root -p
[ ] 内的参数可省略,若连接本地MySQL,则无需指定
概念 | 说明 |
---|---|
数据库DataBase(DB) | 有组织地存储数据的仓库 |
数据库管理系统DataBase Management System(DBMS) | 操纵和管理数据库的大型软件 |
结构化查询语言Structured Query Language(SQL) | 关系型数据库统一标准、编程语言 |
主流的DBMS
关系型数据库(Relational Database)是一种基于关系模型的数据库管理系统(DBMS),使用表格(也称为关系)来组织和存储数据
分类 | 说明 |
---|---|
DCL (Data Control Language) | 数据控制语言,用来创建数据库用户、控制数据库的访问权限 |
DDL (Data Definition Language) | 数据定义语言,用来定义数据库对象(数据库,表字段) |
DML(Data Manipulation Language) | 数据操作语言,用来对数据库表中的数据进行增删改 |
DQL(DataQueryLanguage) | 数据查询语言,用来查询数据库中表的记录 |
查询所有数据库
show databases;
创建数据库
create database itcast;
避免重复创建报错
create database if not exists itcast;
创建数据库,并指定字符集
create database itheima default charset utf8mb4;
删除数据库
drop database if exists test;
切换数据库
use itcast;
查询当前数据库
select database();
查询当前数据库所有表
show tables;
创建表
create table tb_user(
-> id int comment ‘编号’,
-> name varchar(50) comment ‘姓名’,
-> age int comment ‘年龄’,
-> gender varchar(1) comment ‘性别’
-> )comment ‘用户表’;
查看表
desc tb_user;
查看表的创建语句
show create table tb_user;
类型 | 字节数 |
---|---|
TINYINT | 1 |
SMALLINT | 2 |
MEDIUMINT | 3 |
INT | 4 |
BIGINT | 8 |
FLOAT | 4 |
DOUBLE | 8 |
DECIMAL | 小数值(精确定点数) |
类型 | 字节数 | 说明 |
---|---|---|
CHAR | 1 | 定长字符串 |
VARCHAR | 2 | 变长字符串 |
TINYBLOB | 1 | 二进制数据 |
TINYTEXT | 1 | 短文本字符串 |
BLOB | 2 | 二进制形式的长文本数据 |
TEXT | 2 | 长文本数据 |
MEDIUMBLOB | 3 | 二进制形式的中等长度文本数据 |
MEDIUMTEXT | 3 | 中等长度文本数据 |
LONGBLOB | 4 | 二进制形式的极大文本数据 |
LONGTEXT | 4 | 极大文本数据 |
类型 | 字节数 | 范围 |
---|---|---|
DATE | 3 | 1000-01-01 至 9999-12-31 |
TIME | 3 | -838:59:59 至 838:59:59 |
YEAR | 1 | 1901 至 2155 |
DATETIME | 8 | 1000-01-01 00:00:00 至 9999-12-31 23:59:59 |
TIMESTAMP | 4 | 1970-01-01 00:00:01 至 2038-01-19 03:14:07 |
修改名称和类型
alter table emp change nickname username varchar(30);
修改类型
alter table emp modify username varchar(20);
删除字段
alter table emp drop username;
修改表名
alter table emp rename to employee;
删除
drop table if exists tb_user;
删除并重新创建(只删除数据,不删除类型)
truncate table employee;
安装、长期使用
安装文章涉及的资源
若driver files安装失败,则Drivers->MySQL,这个位置会有下载提示(下载完成会消失)
#添加数据
#为指定字段添加数据
insert into user(name, age, id) values ('harry',11,1);
#为全部字段添加数据
insert into user values ('potter',22,2);
#添加多条数据
insert into user values ('peter',33,3),('park',44,4);
#修改数据
update user set name='neo',age=12 where id=1;
#删除数据
delete from user where id=1;
#查看表的数据:双击表格 or 如下一行代码
select * from user;
执行顺序:from、where、group by、having、select、order by、limit
#数据准备
create table emp(
id int comment '编号',
workno varchar(10) comment '工号',
name varchar(10) comment '姓名',
gender char(1) comment '性别',
age tinyint unsigned comment '年龄', idcard char(18) comment '身份证号', workaddress varchar(50) comment '工作地址', entrydate date comment '入职时间'
)comment '员工表';
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (1, '00001', '柳岩666', '女', 20, '123456789012345678', '北京', '2000-01-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (2, '00002', '张无忌', '男', 18, '123456789012345670', '北京', '2005-09-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (3, '00003', '韦一笑', '男', 38, '123456789712345670', '上海', '2005-08-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (4, '00004', '赵敏', '女', 18, '123456757123845670', '北京', '2009-12-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (5, '00005', '小昭', '女', 16, '123456769012345678', '上海', '2007-07-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (6, '00006', '杨逍', '男', 28, '12345678931234567X', '北京', '2006-01-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (7, '00007', '范瑶', '男', 40, '123456789212345670', '北京', '2005-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (8, '00008', '黛绮丝', '女', 38, '123456157123645670', '天津', '2015-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (9, '00009', '范凉凉', '女', 45, '123156789012345678', '北京', '2010-04-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (10, '00010', '陈友谅', '男', 53, '123456789012345670', '上海', '2011-01-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (11, '00011', '张士诚', '男', 55, '123567897123465670', '江苏', '2015-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (12, '00012', '常遇春', '男', 32, '123446757152345670', '北京', '2004-02-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (13, '00013', '张三丰', '男', 88, '123656789012345678', '江苏', '2020-11-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (14, '00014', '灭绝', '女', 65, '123456719012345670', '西安', '2019-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (15, '00015', '胡青牛', '男', 70, '12345674971234567X', '西安', '2018-04-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (16, '00016', '周芷若', '女', 18, null, '北京', '2012-06-01');
#基本查询
##查询
select * from emp;
select name,workno,age from emp;
#别名(as可省略)
select workaddress as '工作地址' from emp;
#去重
select distinct workaddress from emp;
#条件查询
select * from emp where age not in (18,20,40) and idcard like '%x';#身份证最后是x
select * from emp where name like '__';#名字有两个字
#聚合函数
select count(idcard) from emp;#16-1=15
select avg(age) from emp;#40.125
select max(age) from emp;#88
select sum(age) from emp where workaddress='西安';#135
#分组查询
#分组前where过滤,分组后having过滤 #
select workaddress,count(*) as address_count from emp where age<45 group by workaddress having address_count >=3;
select workaddress,gender,count(*) '数量' from emp group by gender, workaddress;
#排序查询
#先按age升序,age相同时再按照entrydate降序
select * from emp order by age asc ,entrydate desc ;
#分页查询
#起始索引,展示记录数
select * from emp limit 10,10;#11~16
#查询用户
select * from mysql.user;
#创建用户
create user 'itcast'@'localhost' identified by '123456';#本地主机
create user 'heima'@'%' identified by '123456';#任意主机
#修改密码
alter user 'itcast'@'localhost' identified with mysql_native_password by '1234';
#删除用户
drop user 'itcast'@'localhost';
drop user 'heima'@'%';
#权限控制
#查询权限
show grants for 'heima'@'%';#USAGE
#授予权限,把itcast数据库所有表的所有权限授予heima
grant all on itcast.* to 'heima'@'%';#ALL PRIVILEGES
#撤销权限
revoke all on itcast.* from heima;