To select data from one table based on data from another table

I want to get the unavailable data in one table(schedules table) based on a list of existing data on another table(Classroom)

This is the schedules

CourseCode

Day

ClassroomID-->Fk from Classroom Table (ClassID)

PeriodID

This is the Classroom Table

Capacity

ClassID (PK)

BuildingName

I have thought of using an inner join and then find a NotIn of the results but I really don't know how to go about it

I expect to see all the Buildings which are available on a particular day at a particular period

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