Database Details and PHP - Details About a Query Response (
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Four PEAR DB methods provide you with information on a query result object: numRows(), numCols(), affectedRows(), and
tableInfo()
.
The
numRows()
and
numCols()
methods tell you the number of rows and columns returned from a
SELECT
query:
$howmany = $response->numRows();
$howmany = $response->numCols();
The
affectedRows()
method tells you the number of rows affected by an
INSERT
,
DELETE
, or
UPDATE
operation:
$howmany = $response->affectedRows();
The
tableInfo()
method returns detailed information on the type and flags of fields returned from a
SELECT
operation:
$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);
function a_to_table ($a) {
echo "<html><head><title> Table Info </title></head>";
echo "<table border=1>\n";
foreach ($a as $key => $value) {
echo "<tr valign=top align=left><td>$key</td><td>";
if (is_array($value)) {
a_to_table($value);
} else {
print_r($value);
}
echo "</td></tr>\n";
}
echo "</table>\n";
}
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 the
books
table, 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 the
createSequence()
and
dropSequence()
methods:
$res = $db->createSequence(sequence);
$res = $db->dropSequence(sequence);
The result will be the result object from the create or drop query or
DB_ERROR
if an error occurred.
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