# Limitations

[](https://help.qlik.com/talend/en-US/talend-data-catalog/Content/developer-guide/metadata-query-language-mql/limitations.htm)

## Limitations

1. Some system attributes cannot be used with the OR operator in the WHERE clause. Refer to System Attribute Filters Not Working With OR for a list of such system attributes.

2. System attribute

   > Conditional Labels

   cannot be used as a related object property of Parent or Children in the WHERE clause. It is okay to use Parent.

   > Conditional Labels

   and Children.

   > Conditional Labels

   in the SELECT list.