Mysql03增删改查

Sql – DML、DQL
DML 数据操作语言
 insert - 插入数据
 update - 修改数据
 delete - 删除数据

DQL 数据查询语言
 select

insert - 插入数据
 insert into tb2 values(值1, 值2, 值3)
 insert into tb2(字段3,字段2) values(值3,值2)
 insert into tb2 values(…),(…),(…)
 将一个查询的结果，插入到一个表中
Insert into tb2 select * from …
 另一种批量插入数据方式：
将查询结果，直接创建成一张新表
create table tb3 as select …. from 表名

 单引号：两个单引号转义成一个单引号
Insert into kecheng(name) values(‘I’'m ')
 Sql 注入攻击
…where … password=‘1’ or ‘1’=‘1’

 阻止 sql 注入攻击：
 将用户填写的内容中的单引号，替换成两个单引号
…where … password=‘1’‘or ‘‘1’’=’‘1’

update – 修改数据
 update tb2 set 字段1=值1, 字段2=值2, 字段3=值3 where …
 update tb2 set … where …
order by … limit 5
对指定字段进行排序后，
只修改前5条数据

delete – 删除数据
 delete from tb2 where …
 delete from tb2 where …
order by … limit 5
按指定字段排序，并是删除前 5 行

 清空表：
 delete from tb2;
 truncate table tb2;

select - 查询数据
 select * from tb2;
 select 字段3, 字段1 from tb2;
where 子句
 过滤条件
= 等值过滤
<> 不等过滤

= < <= 比较大小
between … and … >= … and <= …
in(3,78,2,6,1,8) 从指定的一组值中取值
like 字符串模糊查询
% 统配多个字符
_ 统配单个字符
\ 转义符，_ %
not not between and
not in
not like
and 并且
or 或者
is null
is not null null 值过滤

distinct
 去除重复数据
 select distinct job_id from 表名
查询所有job_id的值，去除重复值

 select distinct 字段1,字段2 from ….
去除两个字段组合的重复值

 只在字段列表前出现一次

order by 子句
 排序
 order by 字段1
 order by 字段1,字段2
先按字段1排序，字段1相同时按字段2排序
 asc 升序（默认可以不写）
 desc 降序

order by 字段1 desc
order by 字段1 desc,字段2 asc
 select …（字段名）from…（表名）order by…
 select …（字段名）from…（表名）where…order by…

字段别名
 查询的字段，或表达式结果，可以起别名
 select first_name as fn, salary from …
 select salary*12 as s from ….
 As 可以省略
 where 后面不能使用字段别名
oder by 可以引用别名

select查询结构
select
distinct
from
where
order by
练习

```
  查询结果插入表
```

– 新建tb2表
use test;
drop table if exists tb2;
create table tb2(
id int primary key auto_increment,
name varchar(20)
)engine=innodb charset=utf8;

               --  查询学生姓名，插入 tb2 表
               Insert into tb2(name) select name from xuesheng;
               
               --  将 tb2 表的数据查询出来，再次插入 tb2
               Insert into tb2(name) select name from tb2;

```
  update 测试
```

update xuesheng set age=age+1,banji_id=3
where name=‘王五’;

update xuesheng set age=age+1,banji_id=3
where name=’ 1’ or ‘1’=‘1’; – sql注入

– 年龄最大的2个学生，班级修改成4
update xuesheng set banji_id=4
order by age desc limit 2;
– desc 降续
– limit 2 前两条

```
  准备测试数据
```

d:\hr_mysql.sql

source 命令：执行sql脚本文件

source d:\hr_mysql.sql 末尾不加分号
show databases; hr库
show tables;

```
  查询员工表
```

Select * from employees;

Select
employee_id,
first_name,
salary
from
employees;

```
  薪水大于等于10000的员工
```

select
employee_id,
first_name,
salary
from
employees
where
salary>=10000;

  工种代码（job_id）是 IT_PROG 的员工

select
employee_id,
first_name,
salary,
job_id
from
employees
where
job_id=‘IT_PROG’;
– job_id=‘it_prog’; 大小写不敏感

  上司工号（manager_id）是 100 的员工（100的下属）

select
employee_id,
first_name,
salary,
manager_id
from
employees
where
manager_id=100;

  部门编号（department_id）是 30 的员工(查询30部门的员工)

select
employee_id,
first_name,
salary,
department_id
from
employees
where
department_id=30;

```
  不在 50 部门的员工
```

select
employee_id,
first_name,
salary,
department_id
from
employees
where
department_id<>50;

查询员工 200

select
employee_id,
first_name,
salary
from
employees
where
employee_id=200;

查询 1995-1-1年之前入职

select
employee_id,
first_name,
salary,
hire_date
from
employees
where
hire_date<‘1995-1-1’;

工资小于 3000

select
employee_id,
first_name,
salary
from
employees
where
salary<3000;

薪水范围［5000，8000］

select
employee_id,
first_name,
salary
from
employees
where
salary between 5000 and 8000;
– salary>=5000 and salary<=8000;

10 , 20 , 60 , 90 四个部门中所有员工（ in 过滤）

select
employee_id,
first_name,
salary,
department_id
from
employees
where
department_id in(10,20,60,90);

查询 first_name 中包含 ar 的员工

select
employee_id,
first_name,
salary
from
employees
where
first_name like ‘%ar%’;

查询 first_name 第三个字符是 e 的员工

select
employee_id,
first_name,
salary
from
employees
where
first_name like ‘__e%’;

查询工种（job_id）以 SA 开头的员工

select
employee_id,
first_name,
salary,
job_id
from
employees
where
job_id like ‘sa%’;

姓名中有 en ，且在80 部门中的员工

select
employee_id,
first_name,
last_name,
salary,
department_id
from
employees
where
(first_name like ‘%en%’
or last_name like’%en%’)
and department_id=80;

部门 90 中所有员工，和工种后缀是 CLERK 的员工

select
employee_id,
first_name,
salary,
department_id,
job_id
from
employees
where
department_id=90 or
job_id like ‘%CLERK’;

工资小于3000 和工资大于15000

select
employee_id,
first_name,
salary
from
employees
where
salary not between 3000 and 15000;
– salary<3000 or salary>15000;

没有上司的人
manager_id是null值

select
employee_id,
first_name,
salary,
manager_id
from
employees
where
manager_id is null;

没有部门的员工
department_id 是null

select
employee_id,
first_name,
salary,
department_id
from
employees
where
department_id is null;

有提成的员工
commission_pct不是null值

select
employee_id,
first_name,
salary,
commission_pct
from
employees
where
commission_pct is not null;

查询 job_id

select distinct job_id from employees;

查询 department_id，过滤 null值

select distinct department_id from employees
where department_id is not null;

查询 manager_id，过滤 null值

select distinct manager_id from employees
where manager_id is not null;

查询 department_id, manager_id 组合，过滤 null值
select distinct department_id, manager_id
from employees
where department_id is not null
and manager_id is not null;
薪水从小到大排列
select
employee_id,
first_name,
salary
from
employees
order by
salary;
按部门降序排列，相同部门中，按薪水升序排列
select
employee_id,
first_name,
salary,
department_id
from
employees
order by
department_id desc, salary;
薪水大于等于 10000 的员工，按姓名排序

select
employee_id,
first_name,
last_name,
salary
from
employees
where
salary >=10000
order by
first_name, last_name;

查询所有员工，按部门编号升序排列
相同部门，按first_name升序排列

select
employee_id,
first_name,
salary,
department_id
from
employees
order by
department_id, first_name;

查询 50 和 80 部门的员工，
按工资降序排列，工资相同按工种代码排列
select
employee_id,
first_name,
salary,
department_id,
job_id
from
employees
where
department_id in(50,80)
order by
salary desc, job_id;
姓名连接起来显示
select
employee_id id,
concat(first_name, ’ ', last_name) name,
salary
from
employees;
查询员工id,first_name,月薪,年薪
过滤年薪大于等于 100000，按年薪排序
select
employee_id,
first_name,
salary,
salary12 s
from
employees
where
salary12>=100000 – 不能使用字段别名
order by s; – 可以使用字段别名

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