MySQL - Connection


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MySQL Connection Using MySQL Binary

You can establish the MySQL database using the mysql binary at the command prompt.

Example

Here is a simple example to connect to the MySQL server from the command prompt −

[root@host]# mysql -u root -p
Enter password:******

This will give you the mysql> command prompt where you will be able to execute any SQL command. Following is the result of above command −

The following code block shows the result of above code −

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2854760 to server version: 5.0.9

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

In the above example, we have used root as a user but you can use any other user as well. Any user will be able to perform all the SQL operations, which are allowed to that user.

You can disconnect from the MySQL database any time using the exit command at mysql> prompt.

mysql> exit
Bye

MySQL Connection Using PHP Script

PHP provides mysql_connect() function to open a database connection. This function takes five parameters and returns a MySQL link identifier on success or FALSE on failure.

Syntax

connection mysql_connect(server,user,passwd,new_link,client_flag);

S. No. Parameter & Description
1

server

Optional − The host name running the database server. If not specified, then the default value will be localhost:3306.

2

user

Optional − The username accessing the database. If not specified, then the default will be the name of the user that owns the server process.

3

passwd

Optional − The password of the user accessing the database. If not specified, then the default will be an empty password.

4

new_link

Optional − If a second call is made to mysql_connect() with the same arguments, no new connection will be established; instead, the identifier of the already opened connection will be returned.

5

client_flags

Optional − A combination of the following constants −

  • MYSQL_CLIENT_SSL − Use SSL encryption.

  • MYSQL_CLIENT_COMPRESS − Use compression protocol.

  • MYSQL_CLIENT_IGNORE_SPACE − Allow space after function names.

  • MYSQL_CLIENT_INTERACTIVE − Allow interactive timeout seconds of inactivity before closing the connection.

You can disconnect from the MySQL database anytime using another PHP function mysql_close(). This function takes a single parameter, which is a connection returned by the mysql_connect() function.

Syntax

bool mysql_close ( resource $link_identifier );

If a resource is not specified, then the last opened database is closed. This function returns true if it closes the connection successfully otherwise it returns false.

Example

Try the following example to connect to a MySQL server −

<html>
   <head>
      <title>Connecting MySQL Server</title>
   </head>
   <body>
      <?php
         $dbhost = 'localhost:3306';
         $dbuser = 'guest';
         $dbpass = 'guest123';
         $conn = mysql_connect($dbhost, $dbuser, $dbpass);
         if(! $conn ) {
            die('Could not connect: ' . mysql_error());
         }
         echo 'Connected successfully';
         mysql_close($conn);
      ?>
   </body>
</html>


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