Web студия "GrandView"

Описание

bool mysql_data_seek ( resource result_identifier, int row_number )

Возвращает TRUE в случае успешного завершения или FALSE в случае возникновения ошибки.

mysql_data_seek() перемещает внутренний указатель в результате запроса к ряду с указанным номером. Следующий вызов mysql_fetch_row() вернёт именно его.

Параметр Row_number должен быть значением от 0 до mysql_num_rows - 1.

Замечание: Функция mysql_data_seek() может быть использована только с mysql_query(), но не с mysql_unbuffered_query().

Пример 1. Пример использования mysql_data_seek()

<?php $link = mysql_pconnect("localhost", "mysql_user", "mysql_password") or die("Could not connect: " . mysql_error()); mysql_select_db("samp_db") or die("Could not select database: " . mysql_error()); $query = "SELECT last_name, first_name FROM friends"; $result = mysql_query($query) or die("Query failed: " . mysql_error()); /* получение рядов в обратном порядке */ for ($i = mysql_num_rows($result) - 1; $i >= 0; $i--) { if (!mysql_data_seek($result, $i)) { echo "Cannot seek to row $i: " . mysql_error() . "\n"; continue; } if(!($row = mysql_fetch_object($result))) continue; echo "$row->last_name $row->first_name<br />\n"; } mysql_free_result($result); ?>

См. также mysql_query() и mysql_num_rows().

add a note User Contributed Notes
mysql_data_seek

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