Installation and simple practice of MySQL in ubuntu environment (1)
This article introduces the simple operation of MySQL under ubuntu through two micro projects, from installation to practice, without much to say, directly on the code:
**The first step: Install MySQL: **
1 ), download and install mysql:
sudo apt-get update
sudo apt-get install mysql-server
2 ), configuration properties: sudomysql_secure_installation
3 ), check whether the installation is successful: systemctl status mysql.service;
Step 2: Create a database: firstDB
1 ), enter mysql: sudo mysql –u root –p
2 ), create a database: create database firstDB;
3 ), check whether the creation is successful: show databases;
Step 3: Create a form: email
1 ), enter the database firstDB: use firstDB;
2 ), create a table: createtable email(id int not null primary key,Email varchar(255));
3 ), check whether the creation is successful: show tables;
Step 4: Insert data
1 ), view the properties of the form: desc email;
2 ), insert data:
INSERT INTO email VALUES('1','[email protected]');
INSERT INTO email VALUES('2','[email protected]');
INSERT INTO email VALUES('3','[email protected]');3) View all data in the table: select*from email; 4), query duplicate emails in the email table: select Email from email group by Email having count(Email)>1；
Step 5: Item 2 1), create a table World: CREATE TABLE World(name VARCHAR(50) NOT NULL,continent VARCHAR(50) NOTNULL,area INT NOT NULL,population INT NOT NULL,gdp INT NOT NULL);2) Insert data: 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);3) If the area of a country exceeds 3 million square kilometers, or(Population exceeds 25 million and GDP exceeds 20 million), Then this country is a big country. Write a SQL query to output the names, populations and areas of all major countries in the table: select name,population,area fromworldwhere(population >25000000 and gdp >20000000)or area >3000000;
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