Unit 2 Exploring Databases and SQL

[cheatsheet1999]

Knowledge Check: Relational Algebra 1

1. Given two tuple sets (A with 10 elements and B with 5 elements), what is the maximum number of tuples in the union of these sets?

• 10
• [Correct] 15 (The maximum number of tuples is achieved when there are no common elements between A and B)
• 5
• 50

2. Which mathematical operator must be used in order to display information about students who are majoring in Computer Science but not in Electrical Engineering?

• [Correct] Difference (The difference operator displays the requested information)
• Intersection
• Union
• Cartesian Product

3. Which statement about the selection operator is true?

• [Correct] It filters certain tuples in a relation based on given criteria. (This is the function of the selection operator)
• It filters certain attributes in a relation based on given criteria.
• It requires more than one relation as its input.
• It requires more than one database as its input.

Knowledge Check: Relational Algebra 2

1. Consider a relation, STUDENT, with the following attributes: Name, ID number, Major, Graduation Year, and GPA. Consider a query using this relation: “List the names and ID numbers of students majoring in Computer Science.” Which operator is absolutely necessary for this query?

• Intersection
• Union
• Difference
• [Correct] Projection (The projection operator is necessary to display the two attributes, name, and ID number, in the query)

2. Consider two sets: A with 10 tuples, and B with 5 tuples. What is the maximum number of tuples that the intersection of A and B can have?

• 15
• [Correct] 5 (The number of tuples in the intersection must be less than the minimum number of tuples in A and B)
• 50
• 10

3. What is the ϴ-Join operation used for?

• To join two tuples in the same relation.
• To join two attributes in the same relation.
• To join two databases.
• [Correct] To join two relations in a database.

4. Which statement about the selection operator is correct?

• It displays certain tuples based on given criteria. (This is the output of the selection operator)
• It displays certain attributes based on given criteria.
• It requires more than one relation.
• It requires more than one attribute.

Unit 1 & 2: Graded Quiz

1. Which of the following is NOT one of the levels of abstraction for databases?

• Physical Schema
• Conceptual Schema
• [Correct] Filesystem Schema
• Views

2. Table descriptions are an example of ______ level documentation.

• Physical Schema
• Views
• Filesystem Schema
• [Correct] Conceptual Schema

3. A particular query that pulls information from one or more tables is an example of a:

• [Correct] View
• Conceptual Schema
• Physical Schema
• Relation

4. Which of the following database types is most oriented toward storing well-structured data?

• NoSQL Database
• Hadoop
• [Correct] Relational Database
• Spark

5. What major advantage do NoSQL database systems have?

• [Correct] NoSQL database systems can deal with unstructured data
• NoSQL database systems data is highly structured
• NoSQL database systems bundle massive scale well
• NoSQL database systems are good for operational data.

6. In an ER Diagram, a diamond shape indicates what?

• An attribute
• [Correct] A relationship
• A constraint
• An entity

7. A participation constraint is indicated how in an ER diagram.

• A dotted line
• A dashed line
• A line
• [Correct]A bold line

8. Consider the query: ∏𝑎,𝑏(𝜎𝑐=2(𝑧∪𝑦)) What does the query return?

• [Correct] Fields a and b of the rows from z and y where c=2.
• Fields a, b, c or the rows from the intersection of z and y where c=2.
• Fields a,b, and c of the rows from y and z where c=2.
• Fields a and b of the rows from the intersection of z and y where c=2.

9. What does the relational algebra operator ‘x’ indicate?

• The union of the two tables.
• [Correct] All possible pairs from the two tables.
• All pairs from the two tables matched on a specified field.
• The intersection of the two tables.

10. Of the three elements in the basic SQL query, which is the only optional one?

• FROM
• [Correct] DISTINCT
• SELECT
• WHERE

11. Massive scale analytics merely require which type of database system?

• [Correct] Hadoop, Spark, or similar
• MongoDB
• Oracle
• NoSQL

12. The basic formula for an SQL query is:
    [Correct] SELECT, FROM, WHERE
    TARGET, RELATION, DISTINCT
    DISTINCT, FIELD, ID
    DISTINCT FROM QUALIFICATION