Good morning ,
I'm facing a difficulty defining some enty type in this case :
1. You are a systems analyst. You have been assigned to design a database management system (DBMS) for Mechanical Engineering (ME) company. ME orders its parts from two types of vendors-local and non-local vendors. Vendors are tracked by vendor #, name, address, and telephone #. Parts are ordered by means of a purchase order. Local vendors can supply both assembled and sub-parts, while non-local vendors can supply only subparts. For each order, ME would like keep track of information such as order #, quantity ordered, date requested and date shipped. A single part is ordered on each purchase order. A part can be an assembled part or a sub-part. An assembled part can contain two or more sub-parts and each sub-part can be used in two or more assembled parts. Parts should have: part#, description, and cost.
ME has requested that the DBMS that you design should provide capability to list the sub-parts that make up an assembled part and from
which vendor it is ordered.
I have identified the following entity types :
But its mentioned that vendors have 2 types :local and non local
the same is for the parts : assembled and subparts.
Should I add a comosite attirbute to both of the relations called : type ?
Another question is : If an attribute exists in a relationship and it's a primary key in an entity type that is particpating in the this relationship , what should i do in this case while creating the relational table for the relationship?
thanks in advance :)