Case Study: Gracie Music Learning Centre Gracie Music Learning Centre offers a wide variety of lessons on different musical instruments. It started its business in $2005,$ and the operational data is stored in a relational database. The system includes information about the lessons, the instruments used in the lessons, the instructors, as well as the students. The Entity$-$Relationship Diagram $($ERD$)$ of the operational database is shown as follows: Figure $1$: ERD of Gracie Music Learning Centre$$s existing operational database The instructor details are recorded in the INSTRUCTOR table. The details consist of Instructor$$s ID$,$ first name, last name, phone, and qualification. The Qualification in the INSTRUCTOR table indicates the highest qualification of the instructor. The LESSON table contains information about the lessons operated by Gracie Music Learning Centre. The table includes lesson ID$,$ instrument ID$,$ instructor ID$,$ class level, class size, and monthly fee. The Class$\_$Size records the maximum number of students within the lesson. All lessons are conducted on a weekly basis. The INSTRUMENT table records all instruments taught by the instructors at Gracie Music Learning Centre. This table contains instrument ID and description. In the ENROLLMENT table, Lesson$\_$Day indicates the day when the lesson takes place $($e$.$g$.$ Monday, Tuesday, etc.$),$ while Lesson$\_$Time shows the lesson time. Start$\_$Date in the ENROLLMENT table indicates the date when the enrollments start, which normally takes place on the first day of the