REASONS WHY NULL VALUES MIGHT BE INTRODUCED INTO THE DATABASE

By

Explain the concept of physical data independence and its importance in database systems (4

points)

 

2. Explain what problems are caused by the design of the following table. (4 points)

 

The Customer table

 

3. List four significant differences between a file-processing system and a DBMS. (4 points)

 

4. Describe the differences in meaning between the terms relation and relation schema. (4

points)

 

5. List two reasons why null values might be introduced into the database. (4 points)

 

6. Write the following queries in SQL, using the university schema

(https://codex.cs.yale.edu/avi/db-book/university-lab-dir/sample_tables-dir/DDL.sql) and

execute your SQL statement on the sample database with small relations

(https://codex.cs.yale.edu/avi/db-book/university-lab-dir/sample_tables-

dir/smallRelations/smallRelationsInsertFile.sql) and show me both the SQL statements and the

query results. (20 points, 4 points each)

a. Find the titles of courses in the Comp. Sci department that have 4 credits.

b. Find the name(s) of the instructor(s) who DON’T earn the lowest salary in the Physics

department.

c. Find the enrollment of each section (number of students enrolled) that was offered in Fall

2017.

d. Find the minimum enrollment, across all sections offered in Fall 2017.

e. Find the course ID and section ID of the sections that had the minimum enrollment in Fall

2017.

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