Details About a Query Response - PHP

Picking up from where we left off last week, we'll be discussing shortcuts, query responses, metadata, and more. This article is excerpted from chapter eight of the book Programming PHP, Second Edition, written by Kevin Tatroe, Rasmus Lerdorf, and Peter MacIntyre (O'Reilly, 2006; ISBN: 0596006810). Copyright © 2006 O'Reilly Media, Inc. All rights reserved. Used with permission from the publisher. Available from booksellers or direct from O'Reilly Media.

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June 28, 2007

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TOOLS YOU CAN USE

Four PEAR DB methods provide you with information on a query result object: numRows(), numCols(), affectedRows(), andtableInfo().

ThenumRows()andnumCols()methods tell you the number of rows and columns returned from aSELECT query:

$howmany = $response->numRows();
$howmany = $response->numCols();

TheaffectedRows()method tells you the number of rows affected by anINSERT,DELETE, orUPDATE operation:

$howmany = $response->affectedRows();

ThetableInfo()method returns detailed information on the type and flags of fields returned from aSELECToperation:

$info = $response->tableInfo();

The following code dumps the table information into an HTML table:

// connect
   require_once('DB.php');
   $db = DB::connect("mysql://librarian:passw0rd@localhost/ library");
   if (DB::iserror($db)) {
     die($db->getMessage());
   }

$sql = "SELECT * FROM BOOKS";

$q = $db->query($sql);
if (DB::iserror($q)) {
die($q->getMessage());
}

$info = $q->tableInfo();
a_to_table($info);

Figure 8-2 shows the output of the table information dumper.

Figure 8-2. The information from tableInfo( )

Sequences

Not every RDBMS has the ability to assign unique row IDs, and those that do have wildly differing ways of returning that information. PEAR DB sequences are an alternative to database-specific ID assignment (for instance, MySQL’s AUTO_INCREMENT).

The nextID() method returns the next ID for the given sequence:

$id = $db->nextID(sequence);

Normally you’ll have one sequence per table for which you want unique IDs. This example inserts values into thebookstable, giving a unique identifier to each row:

$books = array(array('Foundation', 1951),
array('Second Foundation', 1953),
array('Foundation and Empire', 1952));

foreach ($books as $book) {
    $id = $db->nextID('books');
    splice($book, 0, 0, $id);
    $db->query('INSERT INTO books (bookid,title,pub_year) VALUES (?,?,?)',
$book);
}

A sequence is really a table in the database that keeps track of the last-assigned ID. You can explicitly create and destroy sequences with thecreateSequence()anddropSequence()methods:

$res = $db->createSequence(sequence);
$res = $db->dropSequence(sequence);

The result will be the result object from the create or drop query orDB_ERRORif an error occurred.

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