CAR PARK table:
CP_Name is a unique name for each car park, hence PK.
CP_Level is an attribute that links this table to Car Park levels, hence FK.
CAR PARK LEVELS table:
CP_Level is a unique identifier for each car park level, hence PK.
CP_Name links this table with CAR PARK table, hence FK.
CAR PARK SPACE table:
Each car park space is unique, hence CP_Space is PK.
Employee_ID links this table to CAR PARK table, hence FK.
CP_Name links this table to EMPLOYEE DETAILS table, hence FK.
EMPLOYEE DETAILS table:
Employee_ID is a unique identifier, hence PK.
I presumed that as the two tables, (CAR PARK and CAR PARK LEVELS), are already linked via CP_Level they don’t need an extra line linking them, for CP_Name.
Can two tables be linked more than once, diagrammatically?
From the case study you provided, I don’t see a need for the CAR PARK LEVELS table. I would just include it in the CAR PARK table:
CAR PARK:
Name
Location
Capacity
Levels
Also, it says In each car park, the spaces are uniquely identified using a space number. - so assuming the CP_Space column is that space number, I don’t think that would make it unique to use as a primary key - two different car parks could have the same space number. I would make it a composite key that uses the CP_Space and CP_Name columns.
