What is the purpose of a database model? Summarize the roles of the application software and a DBMS. Based on the EMPLOYEE, JOB, and ASSIGNMENT relations presented in Figure 9.5, write a sequence of...

Summarize the roles of the application software and a DBMS.

Based on the EMPLOYEE, JOB, and ASSIGNMENT relations presented in

Figure 9.5, write a sequence of relational operations to obtain a list of all

job titles within the personnel department.