Mysql语句条件查询与筛选

window平台：

（管理员）启动数据库：net start mysql

登陆： mysql -u root -p

create database test；

use test；

项目一：查找重复的电子邮箱

CREATE TABLE email (

ID INT NOT NULL PRIMARY KEY,

Email VARCHAR(255)

)

INSERT INTO email VALUES('1','[email protected]');

INSERT INTO email VALUES('2','[email protected]');

INSERT INTO email VALUES('3','[email protected]');

语句：

select Email from email

group by

Email

having

count(Email) > 1;

项目二：查找大国

-- 创建表

CREATE TABLE World (

name VARCHAR(50) NOT NULL,

continent VARCHAR(50) NOT NULL,

area INT NOT NULL,

population INT NOT NULL,

gdp INT NOT NULL

);

-- 插入数据

INSERT INTO World VALUES( 'Afghanistan', 'Asia',652230,25500100,20343000);

INSERT INTO World VALUES( 'Albania', 'Europe' ,28748,2831741,12960000);

INSERT INTO World VALUES( 'Algeria', 'Africa' ,2381741,37100000,188681000);

INSERT INTO World VALUES( 'Andorra' , 'Europe' ,468,78115,3712000);

INSERT INTO World VALUES( 'Angola' , 'Africa' ,1246700,20609294,100990000);

语句：

select name population area from

World where

population > 25000000 or

area > 3000000 or

gdp > 20000000;