What's the Most Efficient Way to Get an Accurate Row Count Using PDO in PHP?

Accurate Row Count with PDO in PHP

Determining the row count in a database query is crucial for many applications. With the introduction of PDO (PHP Data Objects), there have been some discrepancies regarding the best approach for retrieving row counts. Let's explore the most efficient methods.

Avoiding fetchAll() with Large Datasets

While fetchAll() is a convenient method for retrieving all results from a query, it's not ideal for large datasets where memory usage is a concern. If only the row count is needed, an alternative approach is preferred.

Retrieving Row Count Without Data

When the actual data is not required, the following approach is recommended:

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

This query directly retrieves the row count without fetching the data itself, saving memory.

PDOStatement::rowCount()

For obtaining the row count along with the fetched data, PDO provides PDOStatement::rowCount(). In MySQL, this method works effectively with buffered queries, which are enabled by default. However, its reliability is not guaranteed for other database drivers.

Using PDO::query()

If a query does not contain any variables, a more concise approach is to use PDO::query() instead of a prepared statement:

$nRows = $pdo->query('select count(*) from blah')->fetchColumn();
echo $nRows;

This method eliminates the need for a separate $result variable and simplifies the code.

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