-PC types m:m employees (PC tests)
-CPU types 1:m PC types
-hard drive types 1:m PC types
-motherboard types 1:m PC types
-power supply types 1:m PC types
-ram types 1:m PC types
-customers 1:m orders
-employees
-orders m:m pc_type, peripherals
-pc_type_order_details -peripheral_order_details