如何获取可能受UPDATE影响的行数？

Question

Getting the number of rows affected by a MySQL update is one thing, but how do I get the number of matching rows for an UPDATE query? Otherwise put, the number of rows that COULD have been affected by the update query, even if the data I'm trying to update the rows with is identical to the data already contained within them? Because in this specific case, the DB will not overwrite the data with, so the number of affected rows is 0. Is there some PDO method that helps, similar to PDOStatement::rowCount() ? I also want to avoid a secondary SQL statement, otherwise the question is pointless.

Answer 1

I wanted to avoid extra queries if possible and fortunately, a colleague of mine pointed out that I can give the PDO instance a particular MySQL driver option that forces the rowCount method to return the number of matches related to the query, instead of the number of affected rows, like so:

$options = array(
    PDO::MYSQL_ATTR_FOUND_ROWS => true    // forces the rowCount() method to return the number of matching rows, not the number of affected rows
);   
$connection = new PDO("mysql:host=$db_host;dbname=$db_name", $db_user, $db_pass, $options);