### Filtering the fields of a query

You can specify certain criteria for the fields of a query to be retrieved from the database via a filter, so that when you build reports on the query, the returned results will be narrowed down. In addition, you can also apply sub-queries to a filter. You can type your filter criteria both in the format of a filter and a QBE (Query By Example). The overall conditions will include them both. Always come to SQL to view your conditions.

Note: If a query uses a parameter in its search criteria, you can decide what the query does in case that the parameter value is NULL at runtime (for example, not provided). You can choose to remove the parameter condition from the query's criterion, or treat the parameter value as a default value (0) or an empty string, which can cause great difference in your report result.

To remove the parameter condition from a query if this happens, check Ignore Predicate If Parameter Value Is Null on the Query menu.

For string type parameters, when the value is left blank, if the Ignore Predicate If Parameter Value Is Null is checked, the value of this parameter will be considered as NULL, and this predicate will not appear in the where clause; if not checked, it will be treated as an empty string ("").

- Filtering with the QBE format
- Filtering with the filter format
- Using sub-queries in filters