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show databases ;
# 切换数据库
use db01;
# 当前正使用的数据库
select database();
create database db02;
# ------------------>DDL 表操作 <------------------------
# 创建表
create table user(
id int comment '用户id,唯一标识',
username varchar(50) comment '用户名',
name varchar(50) comment '姓名',
age int comment '年龄',
gender char(1) comment '性别'
) comment '用户信息表';
drop table user;
# 创建表（约束）
create table user(
id int primary key auto_increment comment '用户id,唯一标识', -- 主键约束 auto_increment
username varchar(50) not null unique comment '用户名', -- 非空唯一
name varchar(50) not null comment '姓名', -- 非空
age int comment '年龄',
gender char(1) default '男' comment '性别' -- 默认值
) comment '用户信息表';
create table emp(
id int unsigned primary key auto_increment comment '员工id,唯一标识',
username varchar(50) not null unique comment '用户名',
password varchar(50) default '123456' comment '密码',
name varchar(50) not null comment '姓名',
gender tinyint unsigned not null comment '性别,1:男,2:女',
phone char(11) not null comment '手机号',
job tinyint unsigned comment '职位,1:员工,2:经理,3:老板',
salary int unsigned comment '薪资',
entry_date date comment '入职时间',
image varchar(100) comment '员工头像',
create_time timestamp default current_timestamp comment '创建时间'
);
# 查看当前数据库所有表
show tables;
# 查看表结构
desc user;
# 查看建表语句
show create table user;
# 添加qq字段
alter table user add qq varchar(13) comment 'QQ';
# 修改字段类型
alter table user modify qq varchar(15) comment 'QQ';
# 修改字段名
alter table user change qq qq_number varchar(15) comment 'QQ';
# 删除字段
alter table user drop qq_number;
# 修改表名
alter table user rename to employee;
# 删除表
drop table employee;
# DML 数据操作语言
# 1.为emp的username,password,name,gender,phone,字段赋值
insert into emp1(username,password,name,gender,phone)values ('admin', '123456', '管理员', '1', '12345678901');
# 2.为emp表的所有字段插入值
insert into emp1 values(null,'admin1','123456','管理员','1','12345678901',1,5000,'2020-01-01','/static/img/avatar.jpg',null);
# 3.批量为emp表的username password,name,gender,phone字段赋值
insert into emp1(username,password,name,gender,phone)values
('admin2','123456','管理员2','1','12345678902'),
('admin3','123456','管理员3','1','12345678903');
# 4.查询所有数据
# DML-update 更新数据
# 修改语句的条件可以有，也可以没有，如果没有条件，则修改所有数据
update emp1 set username='zhangsan',password='123456',name='张三',gender='1',phone='12345678901' where id=1;
# 将emp所有员工的入职时间 更新为2020-01-01
update emp1 set entry_date='2020-01-01';
# DML-delete 删除数据
# 1.删除id为1的记录
delete from emp1 where id=1;
# 2.删除所有数据
delete from emp1;
# DQL 查询数据
select * from emp1;
create table emp(
id int unsigned primary key auto_increment comment 'ID,主键',
username varchar(20) not null unique comment '用户名',
password varchar(32) not null comment '密码',
name varchar(10) not null comment '姓名',
gender tinyint unsigned not null comment '性别, 1:男, 2:女',
phone char(11) not null unique comment '手机号',
job tinyint unsigned comment '职位, 1:班主任,2:讲师,3:学工主管,4:教研主管,5:咨询师',
salary int unsigned comment '薪资',
image varchar(255) comment '头像',
entry_date date comment '入职日期',
create_time datetime comment '创建时间',
update_time datetime comment '修改时间'
) comment '员工表';
-- 准备测试数据
INSERT INTO emp(id, username, password, name, gender, phone, job, salary, image, entry_date, create_time, update_time)
VALUES (1,'shinaian','123456','施耐庵',1,'13309090001',4,15000,'1.jpg','2000-01-01','2024-04-11 16:35:33','2024-04-11 16:35:35'),
(2,'songjiang','123456','宋江',1,'13309090002',2,8600,'2.jpg','2015-01-01','2024-04-11 16:35:33','2024-04-11 16:35:37'),
(3,'lujunyi','123456','卢俊义',1,'13309090003',2,8900,'3.jpg','2008-05-01','2024-04-11 16:35:33','2024-04-11 16:35:39'),
(4,'wuyong','123456','吴用',1,'13309090004',2,9200,'4.jpg','2007-01-01','2024-04-11 16:35:33','2024-04-11 16:35:41'),
(5,'gongsunsheng','123456','公孙胜',1,'13309090005',2,9500,'5.jpg','2012-12-05','2024-04-11 16:35:33','2024-04-11 16:35:43'),
(6,'huosanniang','123456','扈三娘',2,'13309090006',3,6500,'6.jpg','2013-09-05','2024-04-11 16:35:33','2024-04-11 16:35:45'),
(7,'chaijin','123456','柴进',1,'13309090007',1,4700,'7.jpg','2005-08-01','2024-04-11 16:35:33','2024-04-11 16:35:47'),
(8,'likui','123456','李逵',1,'13309090008',1,4800,'8.jpg','2014-11-09','2024-04-11 16:35:33','2024-04-11 16:35:49'),
(9,'wusong','123456','武松',1,'13309090009',1,4900,'9.jpg','2011-03-11','2024-04-11 16:35:33','2024-04-11 16:35:51'),
(10,'lichong','123456','林冲',1,'13309090010',1,5000,'10.jpg','2013-09-05','2024-04-11 16:35:33','2024-04-11 16:35:53'),
(11,'huyanzhuo','123456','呼延灼',1,'13309090011',2,9700,'11.jpg','2007-02-01','2024-04-11 16:35:33','2024-04-11 16:35:55'),
(12,'xiaoliguang','123456','小李广',1,'13309090012',2,10000,'12.jpg','2008-08-18','2024-04-11 16:35:33','2024-04-11 16:35:57'),
(13,'yangzhi','123456','杨志',1,'13309090013',1,5300,'13.jpg','2012-11-01','2024-04-11 16:35:33','2024-04-11 16:35:59'),
(14,'shijin','123456','史进',1,'13309090014',2,10600,'14.jpg','2002-08-01','2024-04-11 16:35:33','2024-04-11 16:36:01'),
(15,'sunerniang','123456','孙二娘',2,'13309090015',2,10900,'15.jpg','2011-05-01','2024-04-11 16:35:33','2024-04-11 16:36:03'),
(16,'luzhishen','123456','鲁智深',1,'13309090016',2,9600,'16.jpg','2010-01-01','2024-04-11 16:35:33','2024-04-11 16:36:05'),
(17,'liying','12345678','李应',1,'13309090017',1,5800,'17.jpg','2015-03-21','2024-04-11 16:35:33','2024-04-11 16:36:07'),
(18,'shiqian','123456','时迁',1,'13309090018',2,10200,'18.jpg','2015-01-01','2024-04-11 16:35:33','2024-04-11 16:36:09'),
(19,'gudasao','123456','顾大嫂',2,'13309090019',2,10500,'19.jpg','2008-01-01','2024-04-11 16:35:33','2024-04-11 16:36:11'),
(20,'ruanxiaoer','123456','阮小二',1,'13309090020',2,10800,'20.jpg','2018-01-01','2024-04-11 16:35:33','2024-04-11 16:36:13'),
(21,'ruanxiaowu','123456','阮小五',1,'13309090021',5,5200,'21.jpg','2015-01-01','2024-04-11 16:35:33','2024-04-11 16:36:15'),
(22,'ruanxiaoqi','123456','阮小七',1,'13309090022',5,5500,'22.jpg','2016-01-01','2024-04-11 16:35:33','2024-04-11 16:36:17'),
(23,'ruanji','123456','阮籍',1,'13309090023',5,5800,'23.jpg','2012-01-01','2024-04-11 16:35:33','2024-04-11 16:36:19'),
(24,'tongwei','123456','童威',1,'13309090024',5,5000,'24.jpg','2006-01-01','2024-04-11 16:35:33','2024-04-11 16:36:21'),
(25,'tongmeng','123456','童猛',1,'13309090025',5,4800,'25.jpg','2002-01-01','2024-04-11 16:35:33','2024-04-11 16:36:23'),
(26,'yanshun','123456','燕顺',1,'13309090026',5,5400,'26.jpg','2011-01-01','2024-04-11 16:35:33','2024-04-11 16:36:25'),
(27,'lijun','123456','李俊',1,'13309090027',5,6600,'27.jpg','2004-01-01','2024-04-11 16:35:33','2024-04-11 16:36:27'),
(28,'lizhong','123456','李忠',1,'13309090028',5,5000,'28.jpg','2007-01-01','2024-04-11 16:35:33','2024-04-11 16:36:29'),
(29,'songqing','123456','宋清',1,'13309090029',5,5100,'29.jpg','2020-01-01','2024-04-11 16:35:33','2024-04-11 16:36:31'),
(30,'liyun','123456','李云',1,'13309090030',NULL,NULL,'30.jpg','2020-03-01','2024-04-11 16:35:33','2024-04-11 16:36:31');
-- =================== DQL: 基本查询 ======================
-- 1. 查询指定字段 name,entry_date 并返回
select name,entry_date from emp;
-- 2. 查询返回所有字段
select * from emp;
-- 3. 查询所有员工的 name,entry_date, 并起别名(姓名、入职日期)
select name as 姓名,entry_date as 入职日期 from emp;
-- 4. 查询已有的员工关联了哪几种职位(不要重复)
select distinct job from emp;
-- =================== DQL: 条件查询 ======================
-- 1. 查询 姓名 为 柴进 的员工
select * from emp where name = '柴进';
-- 2. 查询 薪资小于等于5000 的员工信息
select * from emp where salary <= 5000;
-- 3. 查询 没有分配职位 的员工信息
select * from emp where job is null;
-- 4. 查询 有职位 的员工信息
select * from emp where job is not null;
-- 5. 查询 密码不等于 '123456' 的员工信息
select * from emp where password != '123456';
select * from emp where password <> '123456';
-- 6. 查询 入职日期 在 '2000-01-01' (包含) 到 '2010-01-01'(包含) 之间的员工信息
select * from emp where entry_date between '2000-01-01' and '2010-01-01';
-- 7. 查询 入职时间 在 '2000-01-01' (包含) 到 '2010-01-01'(包含) 之间 且 性别为女 的员工信息
select * from emp where entry_date between '2000-01-01' and '2010-01-01' and gender = 2;
select * from emp where( entry_date between '2000-01-01' and '2010-01-01') and gender = 2;
-- 8. 查询 职位是 2 (讲师), 3 (学工主管), 4 (教研主管) 的员工信息
select * from emp where job = 2 or job =3 or job = 4;
select * from emp where job in (2,3,4);
-- 9. 查询 姓名 为两个字的员工信息(_:单个字符；%：任意字符)
select * from emp where name like '__';
-- 10. 查询 姓 '李' 的员工信息
select * from emp where name like '李%';
-- 11. 查询 姓名中包含 '二' 的员工信息
select * from emp where name like '%二%';
-- =================== DQL: 分组查询 ======================
-- 聚合函数
-- 1. 统计该企业员工数量 -count
-- count(字段)
select count(id) from emp;
-- count(*)
select count(*) from emp;
-- count(常量)
select count(123) from emp;
-- 2. 统计该企业员工的平均薪资
select avg(salary) from emp;
-- 3. 统计该企业员工的最低薪资
select min(salary) from emp;
-- 4. 统计该企业员工的最高薪资
select max(salary) from emp;
-- 5. 统计该企业每月要给员工发放的薪资总额(薪资之和)
select sum(salary) from emp;
-- 分组
-- 注意：分组之后，select后的字段列表不能随意书写，能写的一般是 分组字段+聚合函数
-- 1. 根据性别分组 , 统计男性和女性员工的数量
select gender,count(*) from emp group by gender;
-- 2. 先查询入职时间在 '2015-01-01' (包含) 以前的员工 , 并对结果根据职位分组 , 获取员工数量大于等于2的职位
select job,count(*) from emp where entry_date >= '2015-01-01' group by job having count(*) >= 2;
-- =================== 排序查询 ======================
-- 1. 根据入职时间, 对员工进行升序排序
select * from emp order by entry_date asc;
-- 2. 根据入职时间, 对员工进行降序排序
select * from emp order by entry_date desc ;
-- 3. 根据 入职时间 对公司的员工进行 升序排序 ， 入职时间相同 , 再按照 更新时间 进行降序排序
select * from emp order by entry_date asc,update_time desc;
-- =================== 分页查询 ======================
-- MySQL中是使用 limit
-- 1. 从起始索引0开始查询员工数据, 每页展示5条记录
select * from emp limit 0,5;
select * from emp limit 5;
-- 2. 查询 第1页 员工数据, 每页展示5条记录
select * from emp limit 0,5;
-- 3. 查询 第2页 员工数据, 每页展示5条记录
select * from emp limit 5,5;
-- 4. 查询 第3页 员工数据, 每页展示5条记录
select * from emp limit 10,5;
-- 页码
-- 起始索引 = (页码-1) * 每页记录数