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Database System Problems
Transcript of Database System Problems
2. What problem would you encounter if you wanted to produce a listing by city? How would you solve this problem by altering the file structure?
6. Looking at the EMP_NAME and EMP_PHONE contents in Figure P1.5, what change(s) would you recommend?
Database System Problems
4. What data redundancies do you detect? How could those redundancies lead to anomalies?
5. Identify and discuss the serious data redundancy problems exhibited by the file structure shown in Figure P1.5.
In this file structure, there are more than one record for each employee. Due to this, there will be difficulty keeping the data integrity, since one piece of info could change for this project but not another. An example could be that phone or charge per hour could be changed for one project but not another, thus resulting in a loss for the company.
7. Identify the various data sources in the file you examined in Problem 5.
5 Fields per record
There is no way to sort by city the way it is now. You could sort by manager field, but it would not be the same. You would have to split the manager address field into multiple fields and one would be the single field of city.
You would have to split the PROJECT_MANAGER field into 2 fields. Those fields would be for the first name (PROJECT_MANAGER_FIRST_NAME) and last name (PROJECT_MANAGER_LAST_NAME), and thus you can sort by last name. Similarly we can split the MANAGER_ADDRESS field into 4 fields for the area code (MANAGER_AREA), city (MANAGER_CITY), state ((MANAGER_STATE), and zip code (MANAGER_ZIP).
Holly B. Parker is listed more than once. Because of that, we could run into issues when we try to read or write from the record since it could end in not accurate information.
Ideally, having two separate tables would be efficient for this type of data. One could be for employee info and one could be for the project. The EMP_NUM could be the primary key for the employees and it could act as the foreign key for the project table. The EMP_PHONE could be on the employee table so it only needs to be updated once. Overall this should get rid of most of the redundancy in the data.
The source seems to be a file that has data on projects, employees, and job data.
8. Given your answer to Problem 7, what new files should you create to help eliminate the data redundancies found in the file shown in Figure P1.5?
Having separate files on the Employees, Projects, Jobs and Charge rate. The employee file would have the names, address, and phone number. The Project file could have the name of the projects, project leader and positions etc…The Jobs file would have the actual charge per hour per job type. And the Charge rate file could have the hours per type of job for each employee since they wouldn’t be the same for each one.
9. Identify and discuss the serious data redundancy problems exhibited by the file structure shown in Figure P1.9.
10. Given the file structure shown in Figure P1.9, what problem(s) might you encounter if building KOM were deleted?
In the TEACHER_LNAME field “Cordoza” is repeated, as well as the TEACHER_FNAME “Maria” and TEACHER_INITIAL FIELDS “L”. This means that the data will have to be inputted multiple times. Maybe putting those fields into one field will solve the issue.
If KOM was deleted, data about Williston, Hawkins, Cordoza and KOM rooms 204E, 123, and 34 would be deleted. The data probably should have been separated in another table.
3. If you wanted to produce a listing of the file contents by last name, area code, city, state, or zip code, how would you alter the file structure?