Index: dbitem.php
===================================================================
--- dbitem.php	(revision 14795)
+++ dbitem.php	(working copy)
@@ -353,12 +353,9 @@
 		$ret = '';
 
 		foreach ($keys_hash as $field => $value) {
-			if ( !preg_match('/\./', $field) ) {
-				$ret .= '(`' . $this->TableName . '`.' . $field . ' = ' . $this->Conn->qstr($value) . ') AND ';
-			}
-			else {
-				$ret .= '(' . $field . ' = ' . $this->Conn->qstr($value) . ') AND ';
-			}
+			$value_part = is_null($value) ? ' IS NULL' : ' = ' . $this->Conn->qstr($value);
+
+			$ret .= '(' . (strpos($field, '.') === false ? '`' . $this->TableName . '`.' : '') . $field . $value_part . ') AND ';
 		}
 
 		return substr($ret, 0, -5);