Drawing E-R Diagrams Companies, identified by Company ID and described by Company Name and Industry Type, hire consultants, identified by Consultant ID and described by Consultant Name and Consultant Specialty. Consultant Specialty is a multivalued attribute. Assume that a consultant can work for only one company at a time, and sometimes they take breaks and are not working for any company. Company can also have multiple consultants working for them, or at times, they have no need of consultants. Draw an ERD for this situation, including the entities, relationships, and proper names for the attributes, primary keys, as well as the names for the relationships.

Situation 1:

Now, consider that each time a consultant works for a company, a contract is written describing the terms for this consultant engagement. Contract is identified by a composite identifier of Company ID, Consultant ID, and Contract Date. The contract should also include the hourly rate at which the consultant is paid. Assuming the consultant can still work for only one company at a time, redraw the ERD for this situation.

Situation 2:

As a final solution, now consider that although a consultant can work for only one company at a time, we now need to keep the complete history of all consulting engagements for each consultant and company for auditing purposes, so that even when the consultant is no longer in the industry or the company is bankrupt, IRS can still track the contract records. Draw an ERD for this final situation.