Cant connect to my SQL database

问题:

So I'm having an issue connecting to MySQL with Java. Heres my code:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;


public class DBAccess {
    private String Host;
    private String User;
    private String Password;

    public DBAccess() throws ClassNotFoundException, SQLException{
    Class.forName("com.mysql.jdbc.Driver");
    Password = "password";
    Host = "jdbc:mysql://localhost/worlddb";
    User = "root";
    @SuppressWarnings("unused")
    Connection connect = DriverManager.getConnection(Host,User,Password);
        System.out.println("Connected!"); 
    }
    public void RetreiveData(){

    }
    public void ChangeData(){
    }

}

The error that I'm getting is Exception in thread "main"

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown database 'worlddb'

http://postimg.org/image/593stjvjx/ in mySQL workbench, my connection name is "worlddb" hostname is Liquidus(which is the localhost)

• socket is MySQL
• Port: 3306

Why is this?

回答1:

There is a difference between name of connection and name of Database,try world, test or sakila from schemas in the picture.

回答2:

connection = DriverManager.getConnection("jdbc:mysql://localhost/worlddb?" +"user=root&password=password");

Try this, I have a connection to mysql db with same connection, you just add ? after the name of the db.

回答3:

Try this it's hopeful for you:

Connection con = null;
Class.forName("com.mysql.jdbc.Driver");
con =DriverManager.getConnection("jdbc:mysql://localhost/worlddb","root","password"); 

回答4:

Make sure that the database what you have mentioned in Host = "jdbc:mysql://localhost/worlddb"; i.e worlddb is correct or not. The name of the database here is CASE SENSITIVE! So, if you try to connect using a database name like "test2" instead of "Test2" , you will get the

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown database 'test2'

Also try using port number too

Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/worlddb", "root", "password");

回答5:

In the above code, port number is missing.

connection = connection=DriverManager.getConnection("jdbc:mysql://localhost:3306/worlddb","root", "password");

default port number of mysql is 3306

回答6:

Are you sure that the DB server is not case sensitive? I mean maybe on the DB server the DB name is WorldDb and you are trying to connect to it by using worlddb (all low lecters).. Try to use the same name or to configure MySQL to be case insensitive

回答7:

Write

"jdbc:mysql://localhost:3306/worlddb"

instead of

"jdbc:mysql://localhost/worlddb"

回答8:

Charaf jra was right i had the same issue.
your schema(schema = Database) is listed as Host = "jdbc:mysql://localhost/worlddb"; If you look at the schemas in the pic you posted https://postimg.cc/image/593stjvjx/
the schema(Database) is world.

回答9:

Take care to not have white spaces and use jdbc:mysql://localhost:3306/dbname