MySQL简单使用一、条件查询

MySQL admin 2年前 (2018-10-23) 112次浏览 0个评论 扫描二维码

【完全分布式Hadoop】(六)MySQL5.7服务端安装,DBA权限设置以及客户端配置

1、数据类型

char 字符 定长,char(10)
varchar 字符串
int 整数
float 单精度
double 双精度
date 日期 年月日
timestamp 年月日 时分秒 时间戳

decimal 通常和费用金钱相关的使用该类型

2、设置用户权限以及客户端的IP

grant all privileges on *.* to 'root'@'%' identified by '123456';
flush priviliges;

3、查看databases以及创建database、切换database

show databases;
create database ruozedata;
use ruozedata;

4、SQL操作类型介绍

DML:insert update delete select
增删改查
DDL:create database/drop database

5、创建表

每张表基本都需要:创建时间、创建者、修改时间、修改者

create table ruozet1(
id int auto_incremen primary key,

name varchar(100),
age int,
address varchar(100),

create_time timestamp default current_timestamp,
create_user varchar(100),
update_time timestamp default current_timestamp on update current_timestamp,
update_user varchar(100)
)ENGING=InnoDB default CHARSET=utf-8;

-- id主键自增长,唯一
-- default current_timestamp创建时默认时间
-- default current_timestamp on update current_timestamp 新增时以及更新时都会写入当前时间

insert into ruozedata (name,age) values ('张三',18);

6、增删改查数据

新增数据
insert into ruozedata(id, name, age) values(1,'zhangsan',18);
修改数据指定id的信息(高危,请检查好where)
update ruozedata set age=20,address='北京' where id = 1;
删除指定id的数据
delete from ruozedata where id = 1;
清空表(高危,请再三确认where条件,必要时可以先做备份)
delete from ruozedata;
查询数据
select id,name,age from ruozedata;

7、例子

以下表全部来自于Oracle官方例子

--部门表
dept部门表(deptno部门编号/dname部门名称/loc地点)

create table dept (
    deptno numeric(2),
    dname varchar(14),
    loc varchar(13)
);

insert into dept values (10, 'ACCOUNTING', 'NEW YORK');
insert into dept values (20, 'RESEARCH', 'DALLAS');
insert into dept values (30, 'SALES', 'CHICAGO');
insert into dept values (40, 'OPERATIONS', 'BOSTON');

--工资等级表
salgrade工资等级表(grade 等级/losal此等级的最低/hisal此等级的最高)
create table salgrade (
    grade numeric,
    losal numeric,
    hisal numeric
);

insert into salgrade values (1, 700, 1200);
insert into salgrade values (2, 1201, 1400);
insert into salgrade values (3, 1401, 2000);
insert into salgrade values (4, 2001, 3000);
insert into salgrade values (5, 3001, 9999);
--员工表
emp员工表(empno员工号/ename员工姓名/job工作/mgr上级编号/hiredate受雇日期/sal薪金/comm佣金/deptno部门编号)
工资 = 薪金 + 佣金
1.表自己跟自己连接
create table emp (
    empno numeric(4) not null,
    ename varchar(10),
    job varchar(9),
    mgr numeric(4),
    hiredate datetime,
    sal numeric(7, 2),
    comm numeric(7, 2),
    deptno numeric(2)
);
insert into emp values (7369, 'SMITH', 'CLERK', 7902, '1980-12-17', 800, null, 20);
insert into emp values (7499, 'ALLEN', 'SALESMAN', 7698, '1981-02-20', 1600, 300, 30);
insert into emp values (7521, 'WARD', 'SALESMAN', 7698, '1981-02-22', 1250, 500, 30);
insert into emp values (7566, 'JONES', 'MANAGER', 7839, '1981-04-02', 2975, null, 20);
insert into emp values (7654, 'MARTIN', 'SALESMAN', 7698, '1981-09-28', 1250, 1400, 30);
insert into emp values (7698, 'BLAKE', 'MANAGER', 7839, '1981-05-01', 2850, null, 30);
insert into emp values (7782, 'CLARK', 'MANAGER', 7839, '1981-06-09', 2450, null, 10);
insert into emp values (7788, 'SCOTT', 'ANALYST', 7566, '1982-12-09', 3000, null, 20);
insert into emp values (7839, 'KING', 'PRESIDENT', null, '1981-11-17', 5000, null, 10);
insert into emp values (7844, 'TURNER', 'SALESMAN', 7698, '1981-09-08', 1500, 0, 30);
insert into emp values (7876, 'ADAMS', 'CLERK', 7788, '1983-01-12', 1100, null, 20);
insert into emp values (7900, 'JAMES', 'CLERK', 7698, '1981-12-03', 950, null, 30);
insert into emp values (7902, 'FORD', 'ANALYST', 7566, '1981-12-03', 3000, null, 20);
insert into emp values (7934, 'MILLER', 'CLERK', 7782, '1982-01-23', 1300, null, 10);

1. 条件 where > < = >= <=

select * from emp where sal > 3000; --大于3000
select * from emp where sal = 5000; --等于5000
select * from emp where sal <> 5000; --不等于5000

2. 模糊查询 like

select * from emp where ename like '%S%'; --查出ename中包含S的数据
select * from emp where ename like 'S%'; --查出ename中S开头的数据
select * from emp where ename like '%S'; --查出ename中S结尾的数据
select * from emp where ename like '_o%'; --第二个字符为o的字符,占位符: _

3. 排序

select * from emp order by sal; --默认升序
select * from emp order by sal asc; --asc升序
select * from emp order by sal desc; --desc降序
select * from emp order by deptno asc,sal desc; --按照deptno升序,按照sal降序

4. 限制多少行

select * from emp limit 10;
select * from emp order by deptno asc,sal desc limit 10;

5. 聚合 (group by) 聚合函数 (sum count avg max min)

select
deptno,sum(sal) sa sumsal
from emp
group by deptno
having sum(sal) > 10000;

--查看各个部门所有的人工资总和

6. group by字段必须出现在select语句中

select
deptno,job,sum(sal) sa sumsal
from emp
group by deptno,job;

-- group by 字段必须出现在select字段

7. 数量 最大值等

select count(*) from emp;
select max(sal) from emp;

8. 组合 顺序

select 
deptno,job,sum(sal) as sumsal 
from emp 
where job = 'SALESMAN' 
group by deptno,job 
having sum(sal) >3000 
order by sum(sal) desc 
limit 1;

9. as别名

sum(sal) as sumsal

10. union

a表
id,name,address
1,zhangsan,zhangsan18
2,lisi,lisi20
3,wangwu,wangwu24
b表
id,name,address
1,zhangsan,zhangsan18
2,lilei,lilei22
3,wangwu,wangwu24

去重复数据

select * from a
union
select * from b;
1,zhangsan,zhangsan18
2,lisi,lisi20
3,wangwu,wangwu24
2,lilei,lilei22

不去重复数据

select * from a
union all
select * from b;

1,zhangsan,zhangsan18
2,lisi,lisi20
3,wangwu,wangwu24
1,zhangsan,zhangsan18
2,lilei,lilei22
3,wangwu,wangwu24
select id,name from a
union all
select id,address from b;

1,zhangsan
2,lisi
3,wangwu
1,zhangsan18
2,lilei22
3,wangwu24

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