SQL一、MySQL簡單使用
1、資料型別
char 字元 定長,char(10) varchar 字串 int 整數 float 單精度 double 雙精度 date 日期 年月日 timestamp 年月日 時分秒 時間戳
decimal 通常和費用金錢相關的使用該型別
2、設定使用者許可權以及客戶端的IP
grant all privileges on *.* to 'root'@'%' identified by '123456';
flush priviliges;
3、檢視databases以及建立database、切換database
show databases;
create database ruozedata;
use ruozedata;
4、SQL操作型別介紹
DML:insert update delete select 增刪改查 DDL:create database/drop database
5、建立表
每張表基本都需要:建立時間、建立者、修改時間、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主鍵自增長,唯一 – default current_timestamp建立時預設時間 – default current_timestamp on update current_timestamp 新增時以及更新時都會寫入當前時間
insert into ruozedata (name,age) values ('張三',18);
6、增刪改查資料
新增資料 insert into ruozedata(id, name, age) values(1,‘zhangsan’,18); 修改資料指定id的資訊(高危,請檢查好where) update ruozedata set age=20,address=‘北京’ where id = 1; 刪除指定id的資料 delete from ruozedata where id = 1; 清空表(高危,請再三確認where條件,必要時可以先做備份) delete from ruozedata; 查詢資料 select id,name,age from ruozedata;
7、例子
以下表全部來自於Oracle官方例子
--部門表
dept部門表(deptno部門編號/dname部門名稱/loc地點)
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');
--工資等級表
salgrade工資等級表(grade 等級/losal此等級的最低/hisal此等級的最高)
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);
--員工表
emp員工表(empno員工號/ename員工姓名/job工作/mgr上級編號/hiredate受僱日期/sal薪金/comm佣金/deptno部門編號)
工資 = 薪金 + 佣金
1.表自己跟自己連線
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);
-
條件 where > < = >= <=
select * from emp where sal > 3000; --大於3000
select * from emp where sal = 5000; --等於5000
select * from emp where sal <> 5000; --不等於5000
-
模糊查詢 like
select * from emp where ename like '%S%';
--查出ename中包含S的資料select * from emp where ename like 'S%';
--查出ename中S開頭的資料select * from emp where ename like '%S';
--查出ename中S結尾的資料select * from emp where ename like '_o%';
--第二個字元為o的字元,佔位符: _ -
排序
select * from emp order by sal;
--預設升序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 -
限制多少行
select * from emp limit 10;
select * from emp order by deptno asc,sal desc limit 10;
-
聚合 (group by) 聚合函式 (sum count avg max min)
select deptno,sum(sal) sa sumsal from emp group by deptno having sum(sal) > 10000;
–檢視各個部門所有的人工資總和 -
group by欄位必須出現在select語句中
select deptno,job,sum(sal) sa sumsal from emp group by deptno,job;
– group by 欄位必須出現在select欄位 -
數量 最大值等
select count(*) from emp;
select max(sal) from emp;
-
組合 順序
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;
-
as別名 sum(sal) as sumsal
-
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
去重複資料
select * from a union select * from b; 1,zhangsan,zhangsan18 2,lisi,lisi20 3,wangwu,wangwu24 2,lilei,lilei22
不去重複資料
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