help in db wrapper class ??

[PHPycho]

I had the following db wrapper class:
db.class.php

<?php
class Db{
	var $linkID;
	var $queryID;		
	/* Open Database linkID */
	function Db(){	
		$this->linkID = mysql_connect(DB_HOST, DB_USER, DB_PASS);
		mysql_select_db(DB_NAME);
	}

}	
function doQuery($sql){			
	$this->queryID = @mysql_query($sql,$this->linkID);						  
	return $this->queryID;
}	

/* Fetch Data as Array */
function doFetchArr(){
	return mysql_fetch_array($this->queryID);
}



function doFetchNum(){
	return mysql_fetch_row($this->queryID);
}		

/* Return the number of fields in the most recently retrieved result */
function getNumCols(){
    return mysql_num_fields($this->queryID);
}

/* Free the Result */
function doFreeResult(){
	return mysql_free_result($this->queryID);
}	

/* Close Database linkID */
function doClose(){
	mysql_close($this->linkID);
}		

}
?>

when i tried to run another query in the loop of one query , it only shows the results of one. For example:

require_once("db.class.php");
$Db = new Db();
$sql = "SHOW TABLES FROM ".DB_NAME;
$result = $Db->doQuery($sql);

while ($row = $Db->doFetchNum()) {
	//$Db1 = new Db();
    echo "Table: {$row[0]}<br />";
	$sql2 = "SELECT * FROM {$row[0]}";
	$result2 = $Db->doQuery($sql2);
	$num_fields = $Db->getNumCols();
	//$Db->doFreeResult();
	for($i = 0; $i < $num_fields; $i++){
		echo mysql_field_name($result2, $i)."<br />";
	}



} 

In above it returns the field names of only one table.
but if we create another instance of Db class inside the loop and use it , it works.

What i want ?
- i want to modify the db wrapper class to avoid such case ie no need to create another object inside the loop for multilevel queries.

thanks in advance to all of you

[Piranha]

As you have built it you store the result from queries in a variable in the class. If you do it this way you have to create another instance of the class. Another way to use it is to store the result outside the class, then you can use the same instance to more than one query. I hope you understand what I mean, otherwise post again and I or someone else will explain it better.

But why do you want to do queries inside a loop that is a result of a query? Normally it is much better to join the tables in one query, then you only need 1 query instead of 100s or more calls to the database.

[PHPycho]

Thanks Mr. Piranha
Now I am clear..
But one more question ?
which one is better ?
1> storing the query result in class variables
2> storing the result outside the class

waiting for the results..
Thanks again

[Piranha]

I don't think that there is one way that is preferred over the other. It all depends how you like it, if you want to create a new instance of a class or if you want to create a new variable. However you do it note that you don't need new connections.

Still my question, why do you want to do nested queries?

[Piranha]

I still wonder why you need nested queries.