PDO行数-等效num_rows

Question

I'm moving PHP code from mysql to ms sql server. This will execute my query:

  $r = $db_conn->prepare($sql);
  $r->execute();

Before I start processing, I need to count how many rows were returned.

old code:

$r->num_rows;

new code:

$rows  = $r->fetchAll(PDO::FETCH_ASSOC);
$rcount = count($rows);

All good, but when I try to access values from 1st row I'm getting nothing...

try {
    $row = $r->fetch(PDO::FETCH_ASSOC);
} catch (Exception $ex) {   
    return 0;
}   

I need to repoint to 1st row in my recordset after doing the count, how can I do this without having to requery the database again?

I'm new to PHP, sorry for dumb and probably obvious question. Thanks in advance.

Answer 1

There isn't a way in PDO to reset the pointer. You could execute the query again, but given that you've already fetched all the data with your call to fetchAll , that is wasteful. Instead, to access the data, simply loop over the $rows array eg

foreach ($rows as $row) {
    // do something
}

Note that if you expect an exception on fetch , it is likely you might get one on fetchAll too, so you should wrap the call to fetchAll in a try/catch block:

try {
    $rows = $r->fetchAll(PDO::FETCH_ASSOC);
} catch (Exception $ex) {   
    return 0;
}   

Answer 2

One possible approach, if you use PHP Driver for SQL Server , is to use PDOStatement::rowCount and client-side cursor . With this type of cursor row count is available after a query is executed, but this type of cursor should be used for small (medium) result sets.

<?php
# Connection
$server    = 'server\instance,port';
$database  = 'master';
$uid       = 'uid';
$pwd       = 'pwd';

# PDO Connection
try {
    # SQL authentication
    $conn = new PDO("sqlsrv:server=$server;Database=$database", $uid, $pwd);
    # Windows authentication
    #$conn = new PDO("sqlsrv:server=$server;Database=$database");
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch( PDOException $e ) {
    die( "Error connecting to SQL Server".$e->getMessage());
}

# Client-side cursor
try {
    $options = array(
        PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL, 
        PDO::SQLSRV_ATTR_CURSOR_SCROLL_TYPE => PDO::SQLSRV_CURSOR_BUFFERED
    );
    $stmt = $conn->prepare("SELECT * FROM master.sys.server_principals", $options);
    $stmt->execute();
    echo 'Row count: '.$stmt->rowCount().'<br>';
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC) ){
        echo 'Login name: '.$row['name'].'<br>';
    }    
} catch( PDOException $e ) {
    die( "Error executing query".$e->getMessage() );
}

# End
$stmt = null;
$conn = null;
?>