Queries :: Check If Period Breakdown Is Complete

I have 2 tables:
-tblServices
-tblPricesPeriods

Each of the tables has fields for:
-StartDate
-EndDate

The logic behind the database is that each service is contracted for certain period, from StartDate until EndDate (if EndDate is not given - null - it means it is a permanent contract). For each service, we need to input prices. As prices may change during time, we may have different prices records for a service - we need to have the service period broken down into subperiods with different prices. So we need StartDate and EndDate for each period for which particular prices are valid (again, if EndDate is not given - null - it means the prices are valid "forever" into the future from the StartDate).

My problem is: I want to have a check that would return the number of services which period (tblServices) is not fully reflected in the prices periods (tblPricesPeriods). Those would be for example:

-gaps between subperiods (subperiod1 finishing 30.09.2014 and subperiod 2 starting 3.10.2014)
-service period (tblServices) limited by EndDate (not null), while prices period for this service (tblPricesPeriods) having null as EndDate
-start date for service (tblServices) earlier than earliest start date for prices periods for this service (tblPricesPeriods)
-...

Preferably, I'd like to use a normal query for that (or set of queries), but I'm opened to other options.