mysql_query function in php

<?php 
  $con= mysql_connect("localhost","root","mysql");
  mysql_select_db("Db_name",$con);

  $res=mysql_query("select *from table_name");

  mysql_close($con);   // closing connection before 开发者_StackOverflowfetching contents.

  while($r=mysql_fetch_array($res)) {
    echo $r['ename'];
  }

?>

This programs works even if i close the connection before fetching contents from the table.

In order get table contents from the $res connection is not necessary ?

Is$res just a program variable ? If so what kind of data structure it is using(associative array ? )

In oracle we have implicit cursor and explicit cursor. Are there any equivalent things in mysql?

In the above program where cursors come into picture ?

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$res in your case is a special type called a "Resource". Simply put it is a collection of the data returned which the mysql_fetch_* functions operate. As such, it can live beyond the connection. Check the documentation for more details.

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The MySQL client library will fetch the whole result set before the call to mysql_query() returns which explains why your code works.

You can use mysql_unbuffered_query() to fetch the rows incrementally in which case you must keep the connection open.

Note that fetching the rows is handled inside the MySQL client code. $res is just an opaque ressource type that represents an internal resultset object (buffered or not). You can only operate on that ressource by passing it to other MySQL functions.

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In order get table contents from the $res connection is not necessary ?

Why did not you try it and see?

Anyway, what is the reason to close connection manually?

Is $res just a program varible ? If so what kind of data structure it is using(associative array ?

Yes, it is a variable. You can see what is inside with var_dump($res);

In oracle we have implicit cursor and explicit cursor.Are there any equivalent things in mysql ? In the above program where cursors come into picture ?

What exact task are you trying to solve?

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As jason said $res is just like a normal variable of type Resource. This variable holds its value even after the mysql connection is closed as it has no connection with the mysql connection.