数据库SQL基本语法+增删改查练习



13:55:58

王春 2015/1/9 13:55:58

create table depts(

dept_id int,

name varchar(10),

description varchar(50)

);

王春 2015/1/9 13:56:07

create table depts(

dept_id int,

name varchar(10),

description varchar(50)

);

王春 2015/1/9 13:56:12

#insert into depts(dept_id,name,description) values(1,'张三','11111111');

#insert into depts(dept_id,name,description) values(2,'李四','222222');

#insert into depts(dept_id,name,description) values(3,'王五','333333');

#delete from depts;

#update depts set description='000000' where dept_id=1;

select * from depts where name='张三';

15:14:56

王建 2015/1/9 15:14:56

-- create table employees(

-- emplyees_id int,

-- name varchar(10),

-- gender CHAR(10),

-- dept_id int,

-- JOIN_time DATETIME,

-- salary DOUBLE,

-- address VARCHAR(10),

-- image BLOB,

-- description varchar(50)

-- );

-- insert into employees VALUES (3,'王五','M',3,'2008-02-20 14:19:53',3000.00,'天津',null,null);

-- insert into employees VALUES (4,'赵六','F',4,'2009-02-20 15:19:53',4500.00,'沈阳',null,null);

-- insert into employees VALUES (5,'钱七','M',5,'2010-02-20 16:19:53',50000.00,'上海',null,null);

-- insert into employees VALUES (6,'孙八','F',6,'2011-02-20 17:19:53',3000.00,'深圳',null,null);

15:32:36

王春 2015/1/9 15:32:36

-- select * from employees where name='王五';

-- select * from employees where name!='王五';

-- select * from employees where salary>3000;

-- select * from employees where salary>=2000 and salary<=5000;

-- select * from employees where salary BETWEEN 2000 and 5000;

-- select * from employees where dept_id=1 or dept_id=3 or dept_id=5;

-- select * from employees where dept_id in (1,3,5);

-- select * from employees where description is not null;

-- select * from employees where name like '王%';

-- select * from employees where gender='M' and JOIN_time>'2008-01-01';

16:25:02

王春 2015/1/9 16:25:02

-- 排序：asc升序（默认）desc降序

select * from employees order by salary desc;

-- 分页：limit startIndex,count startIndex起始数（从0开始）,count显示几条数据

select * from employees order by salary desc limit 0,4;

SELECT * from employees;

SELECT * from employees WHERE name='张三';

SELECT * from employees WHERE name !='张三';

SELECT * from employees where salary>3000;

SELECT * FROM employees where salary BETWEEN 2000 AND 5000;

SELECT * FROM employees where employee_id in(1,3,5);
-- SELECT * FROM employees where employee_id=1 or employee_id=3 or employee_id=5;

SELECT * from employees where dept_description is NOT NULL;

select * from employees where name LIKE '张%';

SELECT * from employees where gender='M' and join_time>'2008-01-01 00:00:00';
-- 条件查询

-- select * from employees WHERE gender='F' and salary>=3000 AND salary<=4000;

-- select * from employees;

-- 去重distinct和重命名as

-- select distinct dept_id as '部门编号' from employees;

-- 求平均数

-- select avg(salary) '部门4的平局工资' from employees where dept_id=4;

-- 求总和

-- select sum(salary) '部门4的总工资' from employees where dept_id=4;

-- 求最大:max() 最小值min()

-- select min(salary) '部门4的最高工资' from employees where dept_id=4;

-- 内连接(排除条件判断以外)

-- select * from depts d,employees e where d.dept_id=e.dept_id;

-- 外连接(左外连接：以左边的表为基准)

-- select e.* from depts d left join employees e on d.dept_id=e.dept_id;

-- 外连接(外连接：以右边的表为基准)

select d.*,e.* from depts d right join employees e on d.dept_id=e.dept_id;