Since we expect users to use our UI's we don't have direct documentation for the libraries we use.
Finding a record for insert or update is done with the addFilter() method and the query object like:
<?php
$UpdateQuery = new WA_MySQLi_Query($localhost_i);
$UpdateQuery->Action = "update";
$UpdateQuery->Table = "yourtable";
$UpdateQuery->bindColumn("updatedcolumn", "s", "".((isset($_POST["textfield"]))?$_POST["textfield"]:"") ."", "WA_DEFAULT");
$UpdateQuery->addFilter("searchcolumn", "=", "i", "1");
$UpdateQuery->execute();
?>