mysql_data_seek

(PHP 4, PHP 5, PECL mysql:1.0)

mysql_data_seek — Muove il puntatore interno del risultato

Descrizione

bool mysql_data_seek ( resource $identificativo_risultato , int $numero_riga )

Restituisce TRUE in caso di successo, FALSE in caso di fallimento.

mysql_data_seek() muove il puntatore di riga interno del risultato MySQL associato all'identificativo specificato per puntare ad un determinato numero di riga. La successiva chiamata a mysql_fetch_row() dovrebbe restituire questa riga.

numero_riga inizia da 0. numero_riga dovrebbe essere un valore nell'intervallo che va da 0 a mysql_num_rows - 1.

Nota: La funzione mysql_data_seek() può essere usata solo insieme a mysql_query(), non con mysql_unbuffered_query().

Example #1 Esempio seek dati MySQL


<?php
    $connessione = mysql_pconnect("localhost", "utente_mysql", "password_mysql")
        or die("Connessione non riuscita: " . mysql_error());

    mysql_select_db("samp_db")
        or die("Selezione del database non riuscita: " . mysql_error());

    $query = "SELECT cognome, nome FROM amici";
    $risultato = mysql_query($query)
        or die("Query fallita: " . mysql_error());

    /* caricamento righe in ordine inverso */
    for ($i = mysql_num_rows($risultato) - 1; $i >= 0; $i--) {
        if (!mysql_data_seek($risultato, $i)) {
            echo "Non si può eseguire il seek alla riga $i: " . mysql_error() . "\n";
            continue;
        }

        if(!($riga = mysql_fetch_object($risultato)))
            continue;

        echo "$riga->cognome $riga->nome<br />\n";
    }

    mysql_free_result($risultato);
?>

Vedere anche: mysql_query(), mysql_num_rows().

mysql_db_name

mysql_create_db

Last updated: Fri, 18 Jul 2008

add a note User Contributed Notes
mysql_data_seek

Daniel
28-Aug-2008 02:59


Here is a simple function to "peek" at the position of the internal pointer in a query result:





<?php


function mysql_pointer_position($result_set) {


        $num_rows = mysql_num_rows($result_set);


        $i = 0;


        while($result = mysql_fetch_array($result_set)) {


            $i++;


        }


        $pointer_position = $num_rows - $i;





//Return pointer to original position


        if($pointer_position <= $num_rows - 1) {


            mysql_data_seek($result_set, $pointer_position);


        }


        return $pointer_position;


    }


?>

Guy Gordon
27-Jun-2007 01:26


I needed to "peek" at the next record in order to see if fetching it would go too far.  So I want to do a fetch, followed by seek(-1).

 

I could find no function to move the internal row pointer relative to it's current position, or to retrieve it as a row number as required by mysql_data_seek().  This limits the function's usefulness to resetting the row to 0, unless you track the row number yourself.



If you use a While loop to step through the results, you can increment a tracking index at the bottom of the loop.  But be sure never to use Continue; which would bypass your index.  And document this restriction for the person who needs to maintain your code.  It's probably better to use a For loop, which makes the index explicit.  



In either case be sure to range check the index when you manipulate it.  E.G. When I "peek" at the next record I must check for index>=count (end of data).  Or if I decrement the index, make sure it does not go negative.  Again, document why you are coding it this way, so the next programmer doesn't "correct" the inelegant code.

30-May-2006 01:52


A helpful note about the 'resource' data type.



Since the 'resource' variable is pointing to a row in a result set at any given time, you can think of it as being passed to this function by reference every time you pass it or assign it to a variable.



<?



$sql = "SELECT * from <table>";

$result = mysql_query($sql);

$temp_result = $result;



while ($row = mysql_fetch_assoc($temp_result)) {

    // do stuff with $row

}



while ($row = mysql_fetch_assoc($result)) {

    // This code will never run because the 'resource' variable is pointing past the end of the result set,

    // even though it was *not* assigned by reference to $result2.

}



?>



Therefore, the following snipits are functionally identical:



<?



// Start snipit 1



$sql = "SELECT * from <table>";

$result = mysql_query($sql);



while ($row = mysql_fetch_assoc($result)) {

    // do stuff with $row

}



mysql_data_seek($result, 0);



while ($row = mysql_fetch_assoc($result)) {

    // do other stuff with $row

}



// Start snipit 2



$sql = "SELECT * from <table>";

$result = mysql_query($sql);

$temp_result = $result;



while ($row = mysql_fetch_assoc($temp_result)) {

    // do stuff with $row

}



mysql_data_seek($result, 0);



while ($row = mysql_fetch_assoc($temp_result)) {

    // do other stuff with $row

}



?>

jonybd at yahoo dot com
27-Jun-2005 05:40


/*

    helpfull for real time databases query 

    - Query one time

    - Retreive data twice from the same query

    - mysql_data_seek *



*/



include("p_MySql_Connection.php");



$v_Query    =     "SELECT f1 from t1";

            

$v_Result     =     mysql_query($v_Query, $v_RS);



/*

    First loop for one single query

*/

while ($row = mysql_fetch_array($v_Result,MYSQL_NUM)) {

    $v_total = $v_total + $row[1];

}

    echo $v_total; 

            



/*

    Retreive data

*/

$v_Re     =     mysql_data_seek($v_Result,0);

if (!$v_Re){

    echo 'MySql data seek Error' .  mysql_error();

}



/*

    Second loop for one single query

*/            

while ($row = mysql_fetch_array($v_Result,MYSQL_NUM)) {

    echo $row[0];



}

arturo_b at hotmail dot com
20-Apr-2005 08:53


hello, this script would be easy to understand for those that are novice in php whose want to understand about this function:



the table "user" have 2 columns "id" and "name".

"user" content:

position 0: "id"=195342481 "name"='Arthur'

position 1: "id"=179154675 "name"='John'

>>position 2<<: "id"=157761949 "name"='April' >>third row<<

position 3: "id"=124492684 "name"='Tammy'

position 4: "id"=191346457 "name"='Mike'



<?php

  mysql_connect("localhost", "root")

  mysql_select_db("test");

  $sql = mysql_query("select * from user");

  mysql_data_seek($sql, 2);

  echo "<table border=1>";

  while ($row = mysql_fetch_row($sql)){

    echo "<tr><td>$row[0]</td><td>$row[1]</td></tr>";

  }

  echo "</tabla>";

?>



explanation:

mysql_data_seek move internal result pointer to the third row of table user. Thus mysql_fetch_row will begin by april�s row.

b.steinbrink at g m x dot de
08-Dec-2004 11:09


to kennethnash1134 at yahoo dot com



your loop can be done like this as well and i guess this is faster:



$r=mysql_query("select user,id,ip from accounts limit 10");



unset($users); // Just to be sure

while($users[] = mysql_fetch_row);

array_pop($users); // Drop the last entry which is FALSE

kennethnash1134 at yahoo dot com
26-Mar-2004 12:12


/*here is a nice function for converting a mysql result row set into a 2d array, a time saver if need small data from several rows, saves you from having to do Alot of queries... would be nice to have this built into PHP future versions :) */



// simple example query

$r=mysql_query("select user,id,ip from accounts limit 10");



//starts the for loop, using mysql_num_rows() to count total

//amount of rows returned by $r

for($i=0; $i<mysql_num_rows($r); $i++){

             //advances the row in the mysql resource $r

    mysql_data_seek($r,$i);

             //assigns the array keys, $users[row][field]

    $users[$i]=mysql_fetch_row($r);

}



//simple, hope someone can use it :)

// -Kenneth Nash

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mysql_db_name

mysql_create_db

Last updated: Fri, 18 Jul 2008