Currently there isn't an easy way to query on constituents that are the primary member of a household. The only way to do this is to create a selection of primary household members - from there you can add the selection to a query so that you're only looking at the primary household members. To this we will follow these steps:
1. Create a new ad-hoc query with the constituent source view
2. The criteria of the query is Households belonging to\household constituent\household members\is primary contact is equal to yes
3. The output of the query is Households belonging to\Household constituent\Household members\Member Record ID
4. Export the results to excel as a .csv file
5. From Analysis, click Import selections. The Import selections page appears.
6. Under Tasks, click Add an import selection.
7. Enter a unique name and description to help identify the selection.
8. In the Record type field, select Constituent
9. Select Show this Selection in the Query Designer.
10. Under Import file information, browse to the *.csv file
11. In the ID column field, select which column of the import file contains the record ID
12. Click Save and Import. The program runs the process to import the *.csv file and generate a selection based on the selected record IDs
Once you have the selection you can have a criteria of Exists in [selection name] equals yes.
It would be much easier to have a criteria of Primary Household member is equal to yes.