When you have a report parameter with a Dropdown (dynamic) editor you may run into situation where some loaded items are inappropriate in context of another report parameter value. Typical situation is a filter for the fields that have parent-child relationship - like country/state, category/product and so on. To address this you may specify dependencies for the dynamic dropdown and in this way filter a Dropdown using another Dropdown.
To illustrate the approach let's assume that we have a cube that contains 2 dimensions with 1:N relationship:
state_province. To add a filter by the corresponding DB columns we need to setup two parameters:
We want users to choose values from the dynamically populated items list so editors should be switched to Dropdown (dynamic):
In this setup Cube ID is empty; this means that current cube is queried to load dropdown items.
filter_state_province we specified a dependency on
filter_countryreport parameter for the query that populates
filter_countryselection this reloads items list for
To get the idea, take a look how dependent dropdowns work in the published report.
Try to choose "US", "United Kingdom", "Germany" countries and check list options for "State/Province":