This would be rather redundant, but it's just an example. First, the data is queried by the survey IDs "PMA2014_BFR1" and "PMA2015_BFR2", but then a filter is applied before the data which is returned, which would only allow "PMA2014_BFR1" to be returned. But such a filter could be applied on all attributes of the data queried or their relations.
Example syntax
This would be rather redundant, but it's just an example. First, the data is queried by the survey IDs "PMA2014_BFR1" and "PMA2015_BFR2", but then a filter is applied before the data which is returned, which would only allow "PMA2014_BFR1" to be returned. But such a filter could be applied on all attributes of the data queried or their relations.