1Z0-006 Relational Data Model Questions and Answers — Questions and Answers
Question 1: In the context of the relational data model, what is the primary purpose of normalization?
- To increase query performance by adding redundant data.
- To reduce data redundancy and improve data integrity. (Correct answer)
- To create a single, large table to simplify data access.
- To enforce security by encrypting all data within the tables.
Correct answer: To reduce data redundancy and improve data integrity.
Normalization is the process of organizing columns and tables in a relational database to minimize data redundancy. Its main goals are to eliminate undesirable characteristics like Insertion, Update, and Deletion Anomalies, thus improving data integrity.
Question 2: A table named 'EMPLOYEES' has columns 'Employee_ID', 'SSN', and 'Email'. All three columns contain unique values for each employee. Which term best describes all three of these columns collectively before one is chosen to uniquely identify records?
- Foreign Keys
- Super Keys
- Primary Keys
- Candidate Keys (Correct answer)
Correct answer: Candidate Keys
Candidate keys are columns or a set of columns that can uniquely identify a record in a table. In this scenario, 'Employee_ID', 'SSN', and 'Email' are all candidates for the primary key because each one uniquely identifies an employee. The primary key is ultimately selected from one of the available candidate keys.
Question 3: Which of the following constraints is used to link a column in a 'child' table to a primary key in a 'parent' table, ensuring that a value can only be inserted in the child table if it already exists in the parent table?
- CHECK
- UNIQUE
- FOREIGN KEY (Correct answer)
- NOT NULL
Correct answer: FOREIGN KEY
A FOREIGN KEY is a key used to link two tables together. It is a field (or collection of fields) in one table, called the child table, that refers to the PRIMARY KEY in another table, the parent table. This constraint enforces referential integrity, ensuring that a row cannot be added to the child table if its foreign key value does not exist in the parent table's primary key.
Question 4: A database designer is modeling a relationship between 'Students' and 'Courses'. A student can enroll in many courses, and a course can have many students. What is the term for this type of relationship cardinality?
- One-to-One
- One-to-Many
- Many-to-Many (Correct answer)
- Recursive
Correct answer: Many-to-Many
A Many-to-Many relationship exists when one record in a table can be associated with one or more records in another table, and vice-versa. In this case, many students can be related to many courses. This is typically implemented in a relational database by using a third table, often called a junction or linking table.
Question 5: Which of the following is a fundamental characteristic of the relational model, stating that each cell at the intersection of a row and column must hold a single, indivisible value?
- Entity Integrity
- Referential Integrity
- Atomicity (Correct answer)
- Durability
Correct answer: Atomicity
Atomicity is a core principle of the relational model, meaning that all values stored in a column must be indivisible. This is a key requirement for a table to be in the First Normal Form (1NF). It prohibits storing multiple values or nested structures within a single cell.
Question 6: In a relational database, what is the correct term for a single row in a table, which represents a single, implicitly structured data item in the table?
- Attribute
- Relation
- Tuple (Correct answer)
- Schema
Correct answer: Tuple
In the formal relational model, a row is called a tuple. A table is called a relation, and a column is called an attribute. A tuple represents a single record or entity within the table.
1Z0-006 Relational Data Model Questions and Answers
In the context of the relational data model, what is the primary purpose of normalization?