Asked  7 Months ago    Answers:  5   Viewed   101 times

There are many conflicting statements around. What is the best way to get the row count using PDO in PHP? Before using PDO, I just simply used mysql_num_rows.

fetchAll is something I won't want because I may sometimes be dealing with large datasets, so not good for my use.

Do you have any suggestions?

 Answers

77
$sql = "SELECT count(*) FROM `table` WHERE foo = ?"; 
$result = $con->prepare($sql); 
$result->execute([$bar]); 
$number_of_rows = $result->fetchColumn(); 

Not the most elegant way to do it, plus it involves an extra query.

PDO has PDOStatement::rowCount(), which apparently does not work in MySql. What a pain.

From the PDO Doc:

For most databases, PDOStatement::rowCount() does not return the number of rows affected by a SELECT statement. Instead, use PDO::query() to issue a SELECT COUNT(*) statement with the same predicates as your intended SELECT statement, then use PDOStatement::fetchColumn() to retrieve the number of rows that will be returned. Your application can then perform the correct action.

EDIT: The above code example uses a prepared statement, which is in many cases is probably unnecessary for the purpose of counting rows, so:

$nRows = $pdo->query('select count(*) from blah')->fetchColumn(); 
echo $nRows;
Wednesday, March 31, 2021
 
Dunc
answered 7 Months ago
64

It seems that PDO::MYSQL_ATTR_FOUND_ROWS is a mysql connection option. Thus, it works only as PDO connection option as well. So, set it up this way

$opt  = array(
    PDO::MYSQL_ATTR_FOUND_ROWS   => TRUE,
    // you may wish to set other options as well
    PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
);
$this->_db = new PDO($dsn,DB_USER,DB_PASS,$opt);
Wednesday, March 31, 2021
 
shivam
answered 7 Months ago
77

Extending PDO would be done like any other class. Would this suit your needs? The only other code change would be having to instantiate this class instead of the PDO class when making your initial connection.

class PDOEx extends PDO
{
    private $queryCount = 0;

    public function query($query)
    {
    // Increment the counter.
        ++$this->queryCount;

    // Run the query.
        return parent::query($query);
    }

    public function exec($statement)
    {
    // Increment the counter.
        ++$this->queryCount;

    // Execute the statement.
        return parent::exec($statement);
    }

    public function GetCount()
    {
        return $this->queryCount;
    }
}
Saturday, May 29, 2021
 
TheFrack
answered 5 Months ago
57
with open(adresse,"r") as f:
    reader = csv.reader(f,delimiter = ",")
    data = list(reader)
    row_count = len(data)

You are trying to read the file twice, when the file pointer has already reached the end of file after saving the data list.

Saturday, June 19, 2021
 
Valdas
answered 4 Months ago
29

Your PDO is configured to emulate prepared queries, whereas mysqli is using true prepared queries.

The prepared query binds the string ''1'' as an integer parameter value. PHP coerces it to an integer using something like intval(). Any string with non-numeric leading characters is interpreted as 0 by PHP, so the parameter value sent after prepare is the value 0.

The fake prepared query uses string interpolation (instead of binding) to add the string ''1'' into the SQL query before MySQL parses it. But the result is similar, because SQL also treats a string with non-numeric leading characters in an integer context as the value 0.

The only difference is what ends up in the general query log when the parameter is bound before prepare versus after prepare.

You can also make PDO use real prepared queries, so it should act just like mysqli in this case:

$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

PS: This may demonstrate a good reason why it's customary to start id values at 1 instead of 0.

Wednesday, August 18, 2021
 
derobert
answered 2 Months ago
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