The Relational Model And Normalization
Name: _____________________
Date: _____________________
Instructions: Answer all questions. Write your answers clearly in the space provided.
Question 1:
Table is synonymous with the term:
A.
record.
B.
relation.
C.
column.
D.
field.
Answer: _________
Question 2:
Which of the following is not a restriction for a table to be a relation?
A.
The cells of the table must contain a single value.
B.
All of the entries in any column must be of the same kind.
C.
The columns must be ordered.
D.
No two rows in a table may be identical.
Answer: _________
Question 3:
For some relations, changing the data can have undesirable consequences called:
A.
referential integrity constraints.
B.
modification anomalies.
C.
normal forms.
D.
transitive dependencies.
Answer: _________
Question 4:
A key:
A.
must always be composed of two or more columns.
B.
can only be one column.
C.
identifies a row.
D.
identifies a column.
Answer: _________
Question 5:
An attribute is a(n):
A.
column of a table.
B.
two dimensional table.
C.
row of a table.
D.
key of a table.
Answer: _________
Question 6:
A relation in this form is free of all modification anomalies.
A.
First normal form
B.
Second normal form
C.
Third normal form
D.
Domain/key normal form
Answer: _________
Question 7:
If attributes A and B determine attribute C, then it is also true that:
A.
A → C.
B.
B → C.
C.
(A,B) is a composite determinant.
D.
C is a determinant.
Answer: _________
Question 8:
A tuple is a(n):
A.
column of a table.
B.
two dimensional table.
C.
row of a table.
D.
key of a table.
Answer: _________
Question 9:
If attribute A determines both attributes B and C, then it is also true that:
A.
A → B.
B.
B → A.
C.
C → A.
D.
(B,C) → A.
Answer: _________
Question 10:
One solution to the multivalued dependency constraint problem is to:
A.
split the relation into two relations, each with a single theme.
B.
change the theme.
C.
create a new theme.
D.
add a composite key.
Answer: _________
Question 11:
In a relation, the order of the columns does not matter.
A.
True
B.
False
Answer: _________
Question 12:
A functional dependency is a relationship between or among attributes.
A.
True
B.
False
Answer: _________
Question 13:
A key is a group of one or more attributes that uniquely identifies a row.
A.
True
B.
False
Answer: _________
Question 14:
Keys made up of two or more attributes are called composite keys.
A.
True
B.
False
Answer: _________
Question 15:
Given the functional dependency R → S , R is called the determinant.
A.
True
B.
False
Answer: _________
Question 16:
Relations are categorized into normal forms according to the referential integrity constraints that they have.
A.
True
B.
False
Answer: _________
Question 17:
A relation is in Boyce-Codd Normal Form (BCNF) if every determinant is a composite key.
A.
True
B.
False
Answer: _________
Question 18:
A functional dependency is always an equation.
A.
True
B.
False
Answer: _________
Question 19:
A relation has cells that hold multi-value entries.
A.
True
B.
False
Answer: _________
Question 20:
In a relation, the rows are sometimes called "fields".
A.
True
B.
False
Answer: _________
Question 21:
In a relation, the order of the rows matters.
A.
True
B.
False
Answer: _________
Question 22:
In a relation, the rows are sometimes called "records".
A.
True
B.
False
Answer: _________
Question 23:
A relation is a two-dimensional table.
A.
True
B.
False
Answer: _________
Question 24:
Any table that meets the definition of a relation is said to be in first normal form.
A.
True
B.
False
Answer: _________
Question 25:
Given the functional dependency R → (S,T) , then it is also true that R → S .
A.
True
B.
False
Answer: _________
Question 26:
A candidate key is a determinant that determines all the other columns is a relation.
A.
True
B.
False
Answer: _________
Question 27:
The only reason for the existence of relations is to store instances of functional dependencies.
A.
True
B.
False
Answer: _________
Question 28:
A relation is in 5NF when multivalued dependencies are isolated in their own relation.
A.
True
B.
False
Answer: _________
Question 29:
The functional dependency R → S means that the value of S can be determined when we are given a value of R.
A.
True
B.
False
Answer: _________
Question 30:
In a relation, the columns are sometimes called "attributes".
A.
True
B.
False
Answer: _________
Question 31:
A primary key is a composite key that was selected to be the main identifier for the relation.
A.
True
B.
False
C.
True
D.
False
E.
True
F.
False
G.
True
H.
False
Answer: _________
Question 32:
Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:
A.
A → B.
B.
A → C.
C.
A → (B,C).
D.
(B,C) → A.
Answer: _________
Question 33:
The different classes of relations created by the technique for preventing modification anomalies are called:
A.
normal forms.
B.
referential integrity constraints.
C.
functional dependencies.
D.
None of the above is correct.
Answer: _________
Question 34:
A relation is in this form if it is in BCNF and has no multivalued dependencies:
A.
second normal form.
B.
third normal form.
C.
fourth normal form.
D.
domain/key normal form.
Answer: _________
Question 35:
Row is synonymous with the term:
A.
record.
B.
relation.
C.
column.
D.
field.
Answer: _________
Question 36:
The primary key is selected from the:
A.
composite keys.
B.
determinants.
C.
candidate keys.
D.
foreign keys.
Answer: _________
Question 37:
Which of the following is a group of one or more attributes that uniquely identifies a row?
A.
Key
B.
Determinant
C.
Tuple
D.
Relation
Answer: _________
Question 38:
When the values in one or more attributes being used as a foreign key must exist in another set of one or more attributes in another table, we have created a(n):
A.
transitive dependency.
B.
insertion anomaly.
C.
referential integrity constraint.
D.
normal form.
Answer: _________
Question 39:
A relation is considered a:
A.
Column.
B.
one-dimensional table.
C.
two-dimensional table.
D.
three-dimensional table.
Answer: _________
Question 40:
In the relational model, relationships between relations or tables are created by using:
A.
composite keys.
B.
determinants.
C.
candidate keys.
D.
foreign keys.
Answer: _________
Question 41:
A functional dependency is a relationship between or among:
A.
tables.
B.
rows.
C.
relations.
D.
attributes.
Answer: _________
Answer Key
1:
B
Solution: - A record in a database table represents a single instance of data, containing values for each field within the table. - A relation in the relational model refers to a table that stores related data in rows and columns. - A column in a table represents a specific attribute or field that holds a particular type of data. - A field is another term for a column in a database table, representing a specific piece of data within a record. Conclusion: The term "table" in a database is synonymous with the term "relation" in the relational model. Therefore, the correct option is Option2: relation.
2:
C
Solution: The correct answer is Option3: The columns must be ordered. In the relational model, the order of columns does not matter for a table to be considered a relation. The other options are indeed restrictions for a table to be a relation.
3:
B
Solution: Option1: referential integrity constraints. Referential integrity constraints ensure that relationships between tables are maintained and that any changes made to data do not result in orphaned records. However, referential integrity constraints do not directly address the issue of undesirable consequences that can arise from changing data in a relation. Option2: modification anomalies. Modification anomalies refer to the undesirable consequences that can occur when data is inserted, updated, or deleted in a relation. These anomalies can include insertion anomalies, update anomalies, and deletion anomalies, which can lead to inconsistencies and errors in the database. Option3: normal forms. Normal forms are a set of guidelines for designing relational databases to minimize redundancy and dependency issues. While normalizing a relation can help reduce the risk of modification anomalies, it does not directly address the consequences that can arise from changing data in a relation. Option4: transitive dependencies. Transitive dependencies occur when a non-prime attribute is functionally dependent on another non-prime attribute in a relation. While transitive dependencies can lead to data redundancy and inconsistency, they are not directly related to the undesirable consequences that can result from changing data in a relation. In conclusion, the correct answer is Option2: modification anomalies. This option best describes the undesirable consequences that can occur when data is changed in a relation, leading to anomalies such as insertion, update, and deletion anomalies.
4:
C
Solution: Option1: A key must always be composed of two or more columns because a composite key is used to uniquely identify a row in a table when a single column key is not sufficient. Option2: A key can only be one column is incorrect because a key can be composed of multiple columns to uniquely identify a row in a table. Option3: A key identifies a row is correct. A key is used to uniquely identify a row in a table and ensure that each row is unique. Option4: A key identifies a column is incorrect. A key is used to identify a row, not a column in a table. In conclusion, the correct option is Option3: identifies a row. A key is used to uniquely identify a row in a table and ensure data integrity.
5:
A
Solution: An attribute is a column of a table . This means that it represents a specific characteristic or property of the entities in the table. Attributes are used to define the structure of a table and store data related to the entities. An attribute is not a two dimensional table . A two dimensional table is a collection of rows and columns, not a single attribute. Attributes are the individual columns within a table that hold specific data values. An attribute is not a row of a table . A row in a table represents a single entity or record, while an attribute represents a specific characteristic of that entity. Attributes are defined at the column level, not the row level. An attribute is not a key of a table . A key is a special type of attribute that uniquely identifies each record in a table. While keys are important for data integrity and indexing, they are not the same as regular attributes. Therefore, the correct option is Option1: column of a table .
6:
C
Solution: Option1: First normal form In the first normal form, all attributes in a relation must have atomic values. This means that each attribute cannot be further divided into smaller components. This helps in eliminating repeating groups and ensures that each attribute contains only a single value. Option2: Second normal form The second normal form builds on the first normal form by ensuring that all non-key attributes are fully functional dependent on the primary key. This means that each attribute in a relation must be dependent on the entire primary key, not just a part of it. This helps in eliminating partial dependencies. Option3: Third normal form The third normal form further refines the normalization process by ensuring that all attributes are dependent only on the primary key and not on other non-key attributes. This helps in eliminating transitive dependencies and ensures data integrity. Option4: Domain/key normal form The domain/key normal form is not a standard form in the normalization process. It refers to a state where all attributes are dependent on the primary key and are in their simplest form. This helps in ensuring data consistency and reducing redundancy. Conclusion: Based on the explanation provided, the option that best fits the description of being free of all modification anomalies is Third normal form . This is because it ensures that all attributes are dependent only on the primary key and not on other non-key attributes, thereby eliminating transitive dependencies and ensuring data integrity.
7:
D
Solution: Option1: A ? C. This option states that attribute A determines attribute C. If attributes A and B together determine attribute C, it is possible that attribute A alone can determine attribute C as well. Option2: B ? C. This option states that attribute B determines attribute C. If attributes A and B together determine attribute C, it is possible that attribute B alone can determine attribute C as well. Option3: (A,B) is a composite determinant. This option suggests that attributes A and B together determine attribute C. This is consistent with the given information that attributes A and B determine attribute C. Option4: C is a determinant. This option implies that attribute C determines other attributes. However, based on the given information that attributes A and B determine attribute C, it is more accurate to say that C is determined by attributes A and B. In conclusion, the correct options based on the given information are Option1: A ? C, Option2: B ? C, and Option3: (A,B) is a composite determinant. Option4: C is a determinant is not accurate in this context.
8:
C
Solution: Option1: A tuple is not a column of a table. A column represents a single attribute or field in a table, while a tuple represents a single record or row in a table. Option2: A tuple is not a two-dimensional table. A table itself is two-dimensional, with rows and columns, while a tuple is a single row within that table. Option3: A tuple is a row of a table. In the relational model, a tuple is a single record that contains data for each attribute or column in the table. It represents a specific instance or entry in the table. Option4: A tuple is not a key of a table. A key is a unique identifier for a tuple or row in a table, but the tuple itself is not the key. Keys can be primary keys, foreign keys, or other types of constraints used to uniquely identify tuples. Conclusion: The correct option is Option3: a tuple is a row of a table in the relational model.
9:
A
Solution: Option1: A ? B. This option states that attribute A determines attribute B. In the given scenario where attribute A determines both attributes B and C, this statement is true. Option2: B ? A. This option states that attribute B determines attribute A. However, in the given scenario where attribute A determines both attributes B and C, this statement is not necessarily true. Option3: C ? A. This option states that attribute C determines attribute A. In the given scenario where attribute A determines both attributes B and C, this statement is not necessarily true. Option4: (B,C) ? A. This option states that attributes B and C together determine attribute A. In the given scenario where attribute A determines both attributes B and C, this statement is not necessarily true. Therefore, the correct option is Option1: A ? B.
10:
A
Solution: Option1: split the relation into two relations, each with a single theme. This option involves breaking down the original relation into two separate relations, each focusing on a single theme. This helps in resolving the multivalued dependency constraint problem by organizing the data more efficiently. Option2: change the theme. Changing the theme of the relation may not always be a feasible solution as it can lead to data inconsistency and loss of information. It is not a recommended approach to resolving multivalued dependency constraints. Option3: create a new theme. Creating a new theme can be a viable solution to the multivalued dependency constraint problem. By introducing a new theme, the data can be organized in a more structured manner, reducing the chances of data redundancy and inconsistency. Option4: add a composite key. Adding a composite key can help in uniquely identifying each record in the relation, thereby addressing the multivalued dependency constraint problem. This approach can ensure data integrity and improve the overall efficiency of the database. In conclusion, the most effective solution to the multivalued dependency constraint problem is to split the relation into two relations, each with a single theme . This approach helps in organizing the data more efficiently and resolving the issue of multivalued dependencies.
11:
A
Solution: Option1: True In a relation, the order of the columns does not matter because each column is identified by its name and not its position in the relation. This is one of the key features of the relational model. Option2: False If the order of the columns in a relation mattered, it would introduce unnecessary complexity and make it difficult to work with the data. The relational model is designed to be simple and flexible, allowing for easy manipulation of data regardless of the column order. Conclusion: The correct option is True . In a relation, the order of the columns does not matter.
12:
A
Solution: Option1: True A functional dependency is indeed a relationship between or among attributes in a relational database. It describes the relationship between the values of one attribute and the values of another attribute in the same table. Option2: False This statement is incorrect. A functional dependency is a fundamental concept in the relational model and is used to ensure data integrity and consistency in a database. It is crucial for database normalization and helps in organizing data efficiently. In conclusion, the correct option is Option1: True as a functional dependency is a relationship between or among attributes in a database.
13:
A
Solution: Option1: True - In the relational model, a key is indeed a group of one or more attributes that uniquely identifies a row. This key is used to ensure that each row in a table is unique and can be used to establish relationships between tables. Option2: False - This statement is incorrect. A key is essential in a relational database to uniquely identify rows, and it is not optional. Without a key, it would be impossible to distinguish one row from another in a table. Conclusion: Based on the explanation provided, the correct option is Option1: True . A key is a group of one or more attributes that uniquely identifies a row in the relational model.
14:
A
Solution: Option1: True - In the relational model, a composite key is a key that is made up of two or more attributes. This means that the combination of these attributes uniquely identifies a tuple in a relation. - Composite keys are commonly used in database design to ensure data integrity and to establish relationships between tables. Option2: False - This statement is incorrect. Keys made up of two or more attributes are indeed called composite keys in the relational model. - Composite keys play an important role in database normalization and help in reducing redundancy and improving data integrity. Conclusion: Based on the explanation provided, the correct option is Option1: True . Keys made up of two or more attributes are called composite keys in the relational model.
15:
A
Solution: Option1: True In the relational model, a determinant is a set of attributes that uniquely determines the values of other attributes in a relation. In this case, the functional dependency R ? S indicates that the values of attribute R uniquely determine the values of attribute S. Therefore, R is indeed the determinant in this scenario. Option2: False If we consider the functional dependency R ? S, where R determines S, then R is indeed the determinant. Therefore, this statement is false. Conclusion: The correct option is Option1: True . In the given functional dependency R ? S, R is called the determinant as it uniquely determines the values of attribute S.
16:
A
Solution: Option1: True Relations are indeed categorized into normal forms based on the referential integrity constraints they adhere to. Normalization is the process of organizing data in a database to minimize redundancy and dependency by dividing large tables into smaller tables and defining relationships between them. The different normal forms, such as 1NF, 2NF, 3NF, and BCNF, are based on specific rules regarding referential integrity constraints. Option2: False This statement is incorrect. Relations are actually categorized into normal forms based on the referential integrity constraints they follow. The level of normalization a relation has achieved is determined by how well it adheres to these constraints. Conclusion: The correct option is Option1: True . Relations are categorized into normal forms according to the referential integrity constraints they have.
17:
A
Solution: Option1: True In the Boyce-Codd Normal Form (BCNF), every determinant must be a candidate key, which means it can uniquely identify each tuple in the relation. If a determinant is a composite key, it means it is made up of multiple attributes that together uniquely identify a tuple. Therefore, if every determinant in a relation is a composite key, then the relation is in BCNF. Option2: False If every determinant in a relation is a composite key, then the relation is in BCNF. Therefore, the statement that a relation is in BCNF if every determinant is a composite key is true. Conclusion: The correct option is True .
18:
B
Solution: Option1: True - In the context of the relational model and normalization, a functional dependency is a relationship between two attributes in a relation. It is represented as X -> Y, where X determines Y uniquely. This relationship is not necessarily an equation but rather a logical statement about the data. Option2: False - A functional dependency is not always an equation. It is a statement about the relationship between attributes in a relation, indicating that the value of one attribute uniquely determines the value of another. It is a fundamental concept in database normalization. Conclusion: - The correct option is False . A functional dependency is not always an equation but a logical relationship between attributes in a relation.
19:
B
Solution: Option1: True In the relational model, a relation is a table where each cell holds a single value. If a cell holds multiple values, it violates the first normal form of database normalization. Therefore, a relation cannot have cells that hold multi-value entries. Option2: False This is the correct answer. A relation in the relational model cannot have cells that hold multi-value entries. Each cell should hold a single value to adhere to the principles of normalization. Conclusion: The correct option is False . A relation cannot have cells that hold multi-value entries in the relational model.
20:
B
Solution: In a relation, the rows are sometimes called "fields". Option1: True - This statement is incorrect. In a relation, the rows are actually called "tuples" or "records", while the columns are called "fields" or "attributes". Option2: False - This statement is correct. In a relation, the rows are not called "fields", they are called "tuples" or "records". The columns are the ones referred to as "fields" or "attributes". Conclusion: The correct option is Option2: False .
21:
B
Solution: Option1: True In the relational model, the order of the rows in a relation does not matter. The rows are considered to be unordered sets of tuples. The primary key is used to uniquely identify each row, and the order in which the rows are stored in the database does not affect the results of queries or operations on the data. Option2: False The correct answer is False . In the relational model, the order of the rows in a relation does not matter. The rows are considered to be unordered sets of tuples. The primary key is used to uniquely identify each row, and the order in which the rows are stored in the database does not affect the results of queries or operations on the data.
22:
A
Solution: In a relation, the rows are sometimes called "records". Option1: True - This statement is true. In the relational model, each row in a table represents a record or a tuple containing data related to a specific entity or object. Option2: False - This statement is incorrect. In the relational model, rows are indeed referred to as records. They store information about individual instances of the entity being represented in the table. Therefore, the correct answer is Option1: True .
23:
A
Solution: Option1: True A relation in the relational model is indeed a two-dimensional table. It consists of rows and columns where each row represents a record and each column represents an attribute or field of that record. Option2: False This statement is incorrect. A relation in the relational model is always represented as a two-dimensional table. In conclusion, the correct option is Option1: True as a relation is indeed a two-dimensional table in the relational model.
24:
A
Solution: Option1: True In the relational model, a table is said to be in first normal form if it meets certain criteria such as having atomic values in each cell, having a unique column for each row, and having a unique name for each column. This ensures that the table does not have any repeating groups of data and each piece of data is uniquely identifiable. Option2: False If a table does not meet the criteria for first normal form, then it is not considered to be in first normal form. This could be due to having repeating groups of data, having composite keys, or having columns that are not uniquely named. In such cases, the table would need to be normalized further to bring it into first normal form. Conclusion: The correct option is Option1: True . Any table that meets the definition of a relation is said to be in first normal form.
25:
A
Solution: Option1: True In the given functional dependency R ? (S,T), it means that the value of R uniquely determines the values of both S and T. Therefore, it is also true that R ? S, as the value of R uniquely determines the value of S. This is a valid implication based on the given functional dependency. Option2: False If R ? (S,T) is true, it does not necessarily mean that R ? S is also true. The functional dependency R ? (S,T) indicates that the value of R uniquely determines both S and T, but it does not specify that R uniquely determines S alone. Therefore, it is not always true that R ? S based on the given functional dependency. In conclusion, Option1: True is the correct answer as the given functional dependency R ? (S,T) implies that R ? S is also true.
26:
A
Solution: Option1: True A candidate key is a set of one or more columns that can uniquely identify a row in a table. It is a determinant that determines all the other columns in a relation. Therefore, this statement is true. Option2: False If a candidate key can uniquely identify a row in a table and determines all the other columns, then this statement is false. A candidate key is essential for maintaining data integrity and ensuring that each row in a table is uniquely identified. In conclusion, the correct option is Option1: True .
27:
A
Solution: Option1: True Relations in the relational model are used to store data in a structured way. Functional dependencies are a key concept in database normalization, which helps in organizing data efficiently. Therefore, the main purpose of relations is indeed to store instances of functional dependencies. Option2: False Relations in the relational model serve a broader purpose than just storing instances of functional dependencies. They are used to represent entities, attributes, and relationships in a database, allowing for data manipulation and retrieval. While functional dependencies play a crucial role in database design, they are not the sole reason for the existence of relations. Therefore, the correct option is Option1: True .
28:
A
Solution: Option1: True - In the relational model, a relation is said to be in 5NF (Fifth Normal Form) when multivalued dependencies are isolated in their own relation. - This means that each multivalued dependency is represented by a separate relation, ensuring data integrity and reducing redundancy. Option2: False - If a relation is not in 5NF, it means that multivalued dependencies are not isolated in their own relation. - This can lead to data anomalies and inconsistencies in the database. Conclusion: Based on the explanation provided, the correct option is Option1: True . A relation is in 5NF when multivalued dependencies are isolated in their own relation to ensure data integrity and reduce redundancy in the database.
29:
A
Solution: Option1: True The statement is correct. In a functional dependency R ? S, the value of S can indeed be determined when we are given a value of R. This is a fundamental concept in the relational model of databases. Option2: False This statement is incorrect. In a functional dependency R ? S, the value of S is dependent on the value of R. Therefore, the statement that the value of S cannot be determined when we are given a value of R is false. Conclusion: The correct option is Option1: True . In a functional dependency R ? S, the value of S can be determined when we are given a value of R. This is a key concept in the relational model and normalization of databases.
30:
A
Solution: Option1: True In the relational model, columns are indeed referred to as attributes. Each attribute represents a specific piece of information about the entity being modeled. For example, in a table representing employees, attributes could include employee ID, name, and department. Option2: False If the statement is false, then columns in a relation are not called attributes. This would go against the standard terminology used in the relational model. Based on the explanation provided, the correct answer is Option1: True .
31:
A, C, E, G
Solution: Option1: True - A primary key is a unique identifier for each record in a table.
- It can be a single attribute or a combination of multiple attributes.
- In the case of a composite key, it is a key that consists of more than one attribute to uniquely identify a record.
- Therefore, a primary key can indeed be a composite key that serves as the main identifier for the relation. Option2: False - This statement is incorrect as explained above.
- A primary key can be a composite key and is often used as the main identifier for a relation. Conclusion: - The correct option is True as a primary key can be a composite key that serves as the main identifier for a relation.
- It can be a single attribute or a combination of multiple attributes.
- In the case of a composite key, it is a key that consists of more than one attribute to uniquely identify a record.
- Therefore, a primary key can indeed be a composite key that serves as the main identifier for the relation. Option2: False - This statement is incorrect as explained above.
- A primary key can be a composite key and is often used as the main identifier for a relation. Conclusion: - The correct option is True as a primary key can be a composite key that serves as the main identifier for a relation.
32:
A
Solution: Option1: A → B. This option states that attribute A determines attribute B. In this scenario, every time attribute A appears, it is matched with the same value of attribute B. This option aligns with the given information. Option2: A → C. This option states that attribute A determines attribute C. However, the given information mentions that every time attribute A appears, it is not matched with the same value of attribute C. Therefore, this option is not true based on the provided data. Option3: A → (B,C). This option states that attribute A determines both attribute B and attribute C. Since attribute A is matched with the same value of attribute B but not the same value of attribute C, this option is not accurate. Option4: (B,C) → A. This option states that attributes B and C together determine attribute A. Since every time attribute A appears, it is matched with the same value of attribute B and not the same value of attribute C, this option is not consistent with the given information.
Therefore, the correct option based on the provided data is Option1: A → B.
Therefore, the correct option based on the provided data is Option1: A → B.
33:
A
Solution: Option1: Normal forms are different levels of organization for a relational database table to reduce redundancy and dependency. Each normal form represents a higher level of normalization, which helps in preventing modification anomalies. Option2: Referential integrity constraints are rules that enforce relationships between tables in a database. They ensure that data is consistent and accurate by preventing actions that would destroy links between tables. Option3: Functional dependencies are relationships between attributes in a database table. They help in understanding how data is related and can be used to determine the normal form of a table. Option4: None of the above is correct. This option implies that the classes of relations created to prevent modification anomalies do not fall under normal forms, referential integrity constraints, or functional dependencies. In conclusion, the different classes of relations created by the technique for preventing modification anomalies are known as normal forms . These normal forms help in organizing data in a relational database to reduce redundancy and dependency, ultimately improving data integrity and consistency.
34:
C
Solution: Option1: second normal form. In the second normal form, all attributes must depend on the entire primary key. This means that there should be no partial dependencies in the relation. However, being in the second normal form does not guarantee the absence of multivalued dependencies. Option2: third normal form. In the third normal form, all attributes must depend only on the primary key and not on any other non-prime attributes. While being in the third normal form helps in reducing redundancy and improving data integrity, it does not necessarily eliminate multivalued dependencies. Option3: fourth normal form. In the fourth normal form, a relation is in BCNF and has no multivalued dependencies. This means that all non-trivial functional dependencies are on superkeys. Therefore, a relation in BCNF with no multivalued dependencies is in the fourth normal form. Option4: domain/key normal form. The domain/key normal form is not a standard normal form in the relational model. It is used to ensure that all attributes are atomic and that there are no repeating groups. While it helps in organizing data, it does not specifically address multivalued dependencies. Conclusion: The correct option is fourth normal form . This is because a relation in BCNF with no multivalued dependencies is considered to be in the fourth normal form.
35:
A
Solution: Option1: record. A record in a database is a complete set of fields that represent a single entity. It contains all the information related to that entity. Option2: relation. In the relational model, a relation is a table that stores data in rows and columns. Each row represents a record, and each column represents a field. Option3: column. A column in a database table represents a single attribute of the entity being stored. It contains the values for that attribute for each record in the table. Option4: field. A field is a single piece of data stored in a database table. It corresponds to a column in the table and represents a specific attribute of the entity being stored. In conclusion, the term "row" is synonymous with Option1: record. In the context of a database, a row represents a single record containing all the information related to a specific entity.
36:
C
Solution: Option1: Composite keys are keys that consist of multiple attributes to uniquely identify a record in a table. The primary key is not selected from composite keys because it is a single attribute or a combination of attributes that uniquely identifies each record in a table. Option2: Determinants are attributes that determine other attributes in a table. The primary key is not selected from determinants because it is the key that uniquely identifies each record in a table, not an attribute that determines other attributes. Option3: Candidate keys are keys that could potentially be selected as the primary key for a table. The primary key is selected from candidate keys because it is the key that is chosen to uniquely identify each record in a table. Option4: Foreign keys are keys that establish a relationship between two tables. The primary key is not selected from foreign keys because it is a key that uniquely identifies records within a single table, not a key used to establish relationships between tables. Conclusion: The primary key is selected from the candidate keys. Candidate keys are keys that could potentially be chosen as the primary key for a table, and the primary key is the key that is ultimately selected to uniquely identify each record in a table.
37:
A
Solution: Key - A key is a group of one or more attributes that uniquely identifies a row in a table. Determinant - A determinant is an attribute in a relation that determines the values of other attributes. Tuple - A tuple is a row in a table that contains a set of attributes. Relation - A relation is a table in a relational database that contains rows and columns. Conclusion: The correct option is Key as it is the group of one or more attributes that uniquely identifies a row in a table.
38:
C
Solution: - Transitive dependency refers to a situation where a non-prime attribute is functionally dependent on another non-prime attribute. - Insertion anomaly occurs when certain attributes cannot be inserted into a table without the presence of other attributes. - Referential integrity constraint ensures that the values in a foreign key column match the values in the primary key of another table, maintaining the relationship between the tables. - Normal form refers to a state of organizing data in a database to reduce redundancy and improve data integrity. In this scenario, the correct answer is referential integrity constraint as it describes the situation where values in one table must exist in another table to maintain the relationship between them.
39:
C
Solution: - A column in a relation represents a single attribute or field in a table. - A one-dimensional table is not a valid concept in the relational model. Tables in the relational model are typically two-dimensional, with rows and columns. - A two-dimensional table is the correct representation of a relation in the relational model. It consists of rows and columns to store data in a structured format. - A three-dimensional table is not a valid concept in the relational model. Relations are typically represented as two-dimensional tables. Therefore, a relation is considered a two-dimensional table .
40:
D
Solution: Option1: Composite keys are keys that consist of multiple attributes that together uniquely identify a record in a table. They are used to create relationships between tables by linking the values of these attributes in different tables. Option2: Determinants are attributes in a relation that uniquely determine the values of other attributes. They are used to establish functional dependencies and help in the normalization process. Option3: Candidate keys are a set of attributes that can uniquely identify a tuple in a relation. They are used to create relationships between tables by ensuring data integrity and uniqueness. Option4: Foreign keys are attributes in a table that refer to the primary key of another table. They are used to establish relationships between tables and enforce referential integrity. In the relational model, relationships between relations or tables are created by using foreign keys . Foreign keys establish a connection between tables by referencing the primary key of another table, ensuring data integrity and enforcing referential constraints.
41:
D
Solution: Option1: A functional dependency is not a relationship between tables. Tables in a relational database store data in a structured format but do not have direct relationships with each other in terms of functional dependencies. Option2: A functional dependency is not a relationship between rows. Rows in a table represent individual records and do not have functional dependencies with each other. Option3: A functional dependency is a relationship between relations. In the relational model, a relation is a table with rows and columns, and functional dependencies describe the relationships between attributes within a relation. Option4: A functional dependency is a relationship between attributes. In the relational model, attributes are the columns in a table, and functional dependencies describe how the values of certain attributes determine the values of other attributes. Conclusion: The correct option is Option4: attributes . Functional dependencies describe the relationships between attributes in a relation in the relational model.