Where to place derived attributes I have an assignment which requires me to design a database. 

I have 3 entity types WARD, BED, and BED_ASSIGMENT (which is the "composite" entity type between BED and WARD). 

The BED primary key consists of the attributes bed_id and ward_id (each ward has bed number 1 for example, so I need ward_id to properly identify it)

My question is:

I have two attributes: total_bed_ count and total_vacant_bed_count. In which entity type should I place them?
Don't store redundant information. Both total_bed_count and total_vacant_bed_count can be queried.

total_bed_count would be something like select count(*) from bed, while total_vacant_bed_count could be queried if you know which beds don't have patients assigned to them, maybe something like select count(*) from bed where patient is null.