/**
* Retrieves the name of the first primary key of a given table
* @param string $table The table
* @return string|null The primary key, or null if none exists
*/
private function getPrimaryKey($table)
{
if (empty($table)) {
throw new \InvalidArgumentException('Invalid table name');
}
$sql = "SHOW KEYS FROM `{$table}` WHERE Key_name = 'PRIMARY';";
$result = $this->db->query($sql)->fetch();
return $result ? $result['Column_name'] : null;
}
