First of all we want to start up mysql:

mysql -u root -p
enter password

Second thing is to create some database.

create database dbname;

Let’s create dbuser with name dbuser on localhost and password userpass.

CREATE USER 'dbuser'@'localhost' IDENTIFIED BY 'userpass';

Following are two types of granting first one grants all permissions on database dbname to user dbuser accessing from localhost. Second version grants only select and insert permissions.

GRANT ALL ON dbname.* TO 'dbuser'@'localhost';
GRANT SELECT, INSERT ON dbname.* TO 'dbuser'@'localhost';

To see what permissions certain user has use following command. Notice that this will show you permissions of admin on localhost.

SHOW GRANTS FOR 'admin'@'localhost';

The following command is a bit more complex, if you have done something wrong this command will revoke all granted privileges. Afterwards select, insert, update and delete on every available database from any source address.

REVOKE ALL PRIVILEGES ON *.* FROM 'dbuser'@'localhost'; REVOKE GRANT OPTION ON *.* FROM 'dbuser'@'localhost'; GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO 'dbuser'@'localhost'WITH MAX_QUERIES_PER_HOUR 0 MAX_CONNECTIONS_PER_HOUR 0 MAX_UPDATES_PER_HOUR 0 MAX_USER_CONNECTIONS 0;

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To install mysql server is squite easy just enter following line in terminal:

sudo apt-get install mysql-server

When installed you can start or stop server by following lines, if it is installed to default location:

sudo /etc/init.d/mysqld start

sudo /etc/init.d/mysqld stop

Restarting server is similar:

sudo /etc/init.d/mysqld restart

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First thing you need is access to the mysql server, I strongly suggest using WAMP or XAMPP for windows based users or LAMP or XAMPP for linux based users. After you install any of these packages you are required to start mysql database server (service). Of course if you want to create some sort of database you should either use command line interface for mysql or phpmyadmin which comes included in packages I suggested before. PhpMyAdmin is used for operating MySQL based database and great learning tool as it for any action you do trough interface you will be able to see SQL code.

Now let’s continue with Java.

To star connection you will require following code:

Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/somedb", "root", "");

The following statement means that you are using java database connection using mysql protocol connecting to somedb meanwhile user with which you connect to database is root and this user is using empty password as it is default in the previously mentioned packages.

When you execute previous statement you are establishing connection to database. On the other hand very important thing is to close connection to database otherwise you will slow down your server and your application will work slowly.

To close connection to database you need to invoke method in Connection object:”

conn.close();

Now let’s say that we have table in the database somedb named students. Table students contains fields student_id, name, surname, citizenship.  To read data from this table we are going to use basic SQL statement.

SELECT * FROM students

Upper statement means that we select all fields that is all columns and rows from table students. Now let’s see how to execute this statement.

PreparedStatement studs = conn.prepareStatement("SELECT * FROM students");

This means that we are preparing statement to be execute trough our established connection. Also if you have googled or binged then you might have noticed that some are using statement instead of preparedstatement. Difference is huge! Not in this particular example but as you get better it is always good to use proper programming from beginning then to start changing something later on when you figure that it is insecure or wrong. Yes the difference is in security just on short notice. In statement you can place trough SQL injection but if you use preparedstatement this will not pass checking or all special characters will be escaped.

Next step is to execute our query!

ResultSet rs = studs.executeQuery();

This represents execution of preparedstatement studs. Returned object is ResultSet from which we are able to obtain data from database.

Now let’s say that you would like read data about student in the first row. You should use following code.

rs.getInt("student_id");
rs.getString("name");
rs.getString("surname");
rs.getString("citizenship");

Using that code you can obtain all data that can be stored in this table. To move on the next record you will use following method:

rs.next();

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