Try it Out 1-2-2 - Version 1

First, make a copy of this document. Click on File Make a copy

You can click on any of the drawings to edit them once you make a copy.

The following link is a file system that tracks student data. We are going to examine why we would use a database instead of a file system. Later in the course you will be using similar data to develop SQL queries from a database.

You have been asked to create a database for an online high school. Currently they are using the following file system to track student information. We will examine the data together and learn about how you would work with the school to develop a database system.

Student Data File System

One goal when creating a database is eliminate the need for data to be repeated. This is known as data redundancy. You are going to identify data redundancy in the student data set. Open the Student Data File System then examine what data are being repeated and make a list of that data: ANSWER

An application uses the student data file to create a student directory. It bases the output of the application on the sort order of the student name. For example when it encounters a new name in the file system then it knows to create a new entry in the directory. Any duplicate names that are together it ignores. But only if the duplicates are grouped together.

One of the instructors has access to this file system and decides to sort the file based on their own name so that they can see what students they will have in their class. They do not know about the outside application accessing the file system based on student sort order.

How would this affect the application that creates the directory? ANSWER

Why does this violate data independence? ANSWER

**Notes** By using a database instead of a file system we can avoid having applications make changes because the characteristics of the data storage changed. A database allows for data independence.

When developing a database we also want to work towards data integrity. Examine the student data on line 2 and 3 then look at line 14 compared to lines 13 and 15. What has happened in the address? How could we avoid this? ANSWER

Under File Make a Copy of the Google Sheet file system. Now try to sort by student last name, then try to sort by the city in address. Why is it difficult? ANSWER

**Notes** When creating a database we want to make sure that one piece of data is being stored in a column so that searchability and sorting are more efficient.

Examine the Employer columns. These columns track who the student works for. A student could have multiple jobs and we may even need to track more than three employers. Why is this a multi value column that we would want to eliminate when creating a database? ANSWER

Should total employers be a stored piece of data? Why or why not? ANSWER

Some of the fields are required (Null values are not allowed) in this set of data. The students name is an example of a required field. Would employer be a required field (Are null values allowed)? Why or why not? ANSWER