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WorksheetsCâu hỏi về cơ sở dữ liệu
Total questions: 139
Worksheet time: 1hrs 12mins
What is a database?
A program consisting of many commands
A matrix
A relationship
A structured set of data stored in a computer
Which statement is correct about the components of a database system?
Data, hardware
Data, hardware, software, and users
Data, software
Data, users
What is the significance of tables in a relational data model?
Each table is called a relation/entity type/file
Each table is called a database
Each table is called an object
Each table is called information
What issues does a database need to address?
Ownership, security, and authorization, data disputes, ensuring safety
Ownership, security, and authorization
Ownership, security, and authorization, data disputes
Ownership
What does the image below describe?
Database table
External level
Database architecture
Layered model
Which statement is correct about structured and unstructured databases?
Structured databases have organized and clear relationships between components, while unstructured databases do not have clear structure
Both structured and unstructured databases have organized and clear relationships between components
Both structured and unstructured databases do not have clear structure
Structured databases do not have clear structure, while unstructured databases do
Who is responsible for organizing the content of the database, creating and granting access rights to users, and protecting data safety in case of incidents?
System analyst and designer
Database administrator
Application programmer
End user
Câu 8: Điểm nào sau đây diễn giải đúng về tính dùng chung của cơ sở dữ liệu ?
A. Cơ sở dữ liệu cho phép nhiều người truy cập và sử dụng dữ liệu mà không bị ảnh hưởng đến người khác
B. Cơ sở dữ liệu giảm bớt chi phí bảo trì hệ thống
C. Cơ sở dữ liệu đảm bảo tính nhất quán và toàn vẹn dữ liệu
D. Cơ sở dữ liệu tăng khả năng phát triển các ứng dụng
Which of the following correctly interprets the common use of databases?
Databases allow multiple users to access and use data without being affected by others
Databases reduce system maintenance costs
Databases ensure data consistency and integrity
Databases increase the ability to develop applications
What does the image below illustrate?
Distributed data model
Network data model
Object-oriented data model
Hierarchical data model
What does the image below illustrate?
Network data model
Object-oriented data model
Inferential data model
Distributed data model
Which data model uses graphs to represent data in the form of entities (keys, attributes) and the relationships between them?
Inferential model
Distributed model
Entity-Relationship model
Object-oriented model
Which data model organizes data in a tree structure, with a root node and hierarchical child nodes?
Hierarchical model
Network model
Relational model
Object-oriented model
Which data model is currently the most widely used, with data organized in tables?
Hierarchical model
Network model
Relational model
Distributed model
A company wants to build a centralized data management system while supporting decision-making based on analyzed data. Which data model is the BEST choice for this company?
Hierarchical model
Relational model
Network model
Inferential model
A system needs to manage a massive amount of data distributed across multiple servers in different geographical areas. The most important requirement of the system is to ensure high availability, allowing continuous data access even if some servers fail. Which data model is INDISPENSABLE to meet this requirement?
Which data model is NOT ESSENTIAL to meet the system's requirements?
Relational model
Object-oriented model
Distributed model
Entity-Relationship model
In which field is the database primarily applied?
Information system management in government agencies
Scientific research
Information processing in enterprises
All of the above
What does the image below describe?
Layered architecture
Hierarchical data model
Network data model
Database management system architecture
When a student accesses the credit registration page to view the schedule, which level in the database architecture does it belong to?
Logical level
External or view level
Physical level
Data analysis level
What does the image below illustrate?
Hierarchical data model
Relational data model
Network data model
Deductive data model
What does the image below describe?
Hierarchical data model
Network data model
Relational data model
Distributed data model
An application needs to manage information about courses, instructors, and students. Each course can have multiple instructors, and each instructor can teach multiple courses. Each student can participate in multiple courses, and each course can have multiple students participating. Which data model is MOST SUITABLE for designing the database for this application?
Hierarchical model
Relational model
Network model
Distributed model
Which statement is correct about the database system?
It is an architecture consisting of multiple layers
It is a multi-layered model
It focuses on creating, maintaining, and using databases
It consists of multiple information cycles
Which component is in the entity-relationship model?
Object
Key
Entity
What is a component in the entity-relationship model?
Object
Key
Entity, attribute, key
Attribute
Which component does Microsoft SQL Server belong to in the database system?
Data
Software
Hardware
User
Which is a database management system?
Packet Tracker
StarUML
Microsoft Word
Microsoft SQL Server 2022
Which data model integrates data storage capabilities with reasoning capabilities to support decision making?
Hierarchical model
Relational model
Object-oriented model
Deductive model
Sales staff access the database to view invoice information and check inventory, so which object do they belong to?
System analyst
Database administrator
Application programmer
End user
What is the English name of the Database Management System?
Random Access Memory
HyperText Markup Language
Database management system
Read-only Memory
Which of the following correctly interprets the shared use of a database?
The database allows multiple users to access and use data without being affected by others
The database reduces system maintenance costs
The database ensures data consistency and integrity
The database increases the ability to develop applications
What does the image below describe?
Relational data model
Distributed data model
Hierarchical data model
Network data model
In a table, each attribute corresponds to which case below?
A data table
A data column
A data row
A data set
The domain of the attribute 'date of birth' usually includes:
Integers
Character strings
Real numbers
Date values
What is the range of the attribute 'date of birth'?
Integers
Character strings
Real numbers
Date values
What is the range of the attribute 'gender' in a dataset?
Male
Female
Male, female
Character strings
How many keys can a relation have?
0
1
2
Many
Given the relation Student(MaSV, TenSV, NgaySinh, Gioitinh, QueQuan). What is the key of the relation?
MaSV
TenSV
NgaySinh
Gioitinh
What is the representation of the subtraction operation?
R - S = { t | t ∈ R and t ∈ S}
R - S = { t | t ∈ R and t ∉ S}
R - S = { t | t ∈ R or t ∈ S}
R - S = { t | t has the form (a1, a2, …, an, b1, b2, …, bm) where {a1, a2, …, an} ∈ R; {b1, b2, …, bm} ∈ S }
Given two relations R and S as follows: R A B C a1 a1 b1 b2 c1 c2 S A B C a1 a2 b2 c2 c2. What is the result of R ∩ S?
R ∩ S = A B C a1 a1 a2 b1 b2 b2 c1 c2 c2
R ∩ S = A B C a1 b2 c2
R ∩ S = A B C a1 a2 b1 b2 c1 c2
R ∩ S = A B C a2 b2 c2
Given two relations R and S as follows: R A B C a1 a2 b1 b2 c1 c2 S D E F d1 d2 e1 e2 f1 f2. What is the result of the Cartesian product R x S?
R x S = A B C D E F a1 a2 b1 b2 c1 c2 d1 d2 e1 e2 f1 f2
R x S = A B C D E F a1 a2 a2 b1 b2 b2 c1 c1 c2 d1 d2 d1 e1 e2 e1 f1 f2 f1
R x S = A B C D E F a1 a1 a2 a2 b1 b1 b2 b2 c1 c1 c2 c2 d1 d2 d2 d2 e1 e2 e2 e2 f1 f2 f2 f2
R x S = A B C D E F a1 a1 a2 a2 b1 b1 b2 b2 c1 c1 c2 c2 d1 d2 d1 d2 e1 e2 e1 e2 f1 f2 f1 f2
Given two relations R and S as follows: R A B C a2 a1 a3 b2 b2 b3 c2 c2 c3 S A B C a1 a2 a1 b2 b2 b2 c2 c2 c1. What is the result of R - S?
R - S = A B C a1 a1 a2 b1 b2 b2 c1 c2 c2
R - S = A B C a1 b2 c2
R - S = A B C a3 b3 c3
R - S = A B C a2 b2 c2
What is the representation of the projection operation?
Πx R={ t | t ∈ R }
Πx R={ t | t ∈ R and t (F) = True }
Πx R={ t u,v | u ∈ R; v ∈ S and satisfies the selection expression F }
Πx R={t.M with
What is the representation of projection?
Пx R=t X t ∈R }
Пx R={ t / t ∈ R and t (F) = True }
Пx R={ t u,v / u ∈ R; v ∈ S and satisfies the expression select F }
Пx R={t.M with t∈R, t.M x S ⊆ R and M = U - V }
What is the representation of division?
R ÷ S =t X t ∈R }
R ÷ S ={ t / t ∈ R and t (F) = True }
R ÷ S ={ t u,v / u ∈ R; v ∈ S and satisfies the expression select F }
R ÷ S ={t.M with t∈R, t.M x S ⊆ R and M = U - V }
What is the projection on the attribute set X of relation R?
Пx R= A B a1 a2 a1 b1 b2 b2
Пx R= B C b1 b2 b2 c1 c2 c1
Пx R= A B C a1 a2 a1 b1 b2 b2 c1 c2 c1
Пx R= A B C a1 a2 b1 b2 c1 c2
What is the result of the division of R and S?
R ÷ S = A B a c b d
R ÷ S = A B a b c b c d
R ÷ S = A B a b
R ÷ S = A B c d
Write the relational algebra expression to find the list of items with yellow color.
ПMauSac="Vàng" (HANGHOA)
ПMaCongTy(σMaHang="H1CUNGCAP)
σMauSac="Vàng" (HANGHOA)
ПMaCongTy(σMaHang="H1CUNGCAP∗CONGTY)
Write the relational algebra expression to find the names of companies supplying the item with code H2.
ПMauSac="Vàng" (HANGHOA)
ПMaCongTy(σMaHang="H2CUNGCAP)
σMauSac="Vàng" (HANGHOA)
ПTenCongTy ∗ MaCongTy(σMaHang="H2CUNGCAP∗CONGTY)
What is the relationship R defined on the attribute set U?
R(U) ⊃ DOM(A1) x DOM(A2) x … x DOM(An)
R(U) = DOM(A1) ∩ DOM(A2) ∩ … ∩ DOM(An)
R(U) = DOM(A1) ∪ DOM(A2) ∪ … ∪ DOM(An)
R(U) ⊆ DOM(A1) x DOM(A2) x … x DOM(An)
What is the range of the attribute 'Score' on a 4-point scale?
Integers from 0 to 10
Real numbers from 0 to 10
A, B, C, D
A, B, C, D, F
What is the representation of the Cartesian product?
R x S = { t | t ∈ R and t ∈ S}
R x S = { t | t ∈ R and t ∉ S}
R x S = { t | t ∈ R or t ∈ S}
R x S = { t | t has the form (a1, a2, …, an, b1, b2, …, bm) where {a1, a2, …, an} ∈ R; {b1, b2, …, bm} ∈ S }
What is the result of R1 ∪ R2?
R1 ∪ R2 MASV MAMH DIEMTHI 1 CSDL 5.0 2 CTDL 6.0 3 Anh1 8.0 3 TTNT 5.0
R1 ∪ R2 MASV MAMH DIEMTHI 1 CSDL 5.0 2 CTDL 6.0
R1 ∪ R2 MASV MAMH DIEMTHI 3 TTNT 5.0 3 Anh1 8.0
R1 ∪ R2 MASV MAMH DIEMTHI 1 CSDL 5.0 3 TTNT 5.0 3 Anh1 8.0
What is the result of R - S?
R - S = A B C a1 a1 a2 b1 b2 b2 c1 c2 c2
R - S = A B C a1 b2 c2
R - S = A B C a1 b1 c1
R - S = A B C a2 b2 c2
What is the representation of the selection operation?
σF R=t X t ∈R }
σF R={ t / t ∈ R and t (F) = True }
σF R={ t u,v / u ∈ R; v ∈ S and satisfies selection expression F }
σF R={t.M where t∈R, t.M x S ⊆ R and M = U - V }
Given two relations R and S as follows: R A B C a1 a2 a3 b1 b2 b3 1 2 3 S C D 2 3 d1 d2 What is the result of the natural join between R and S?
R * S = A B C D a1 a2 b1 b3 1 2 d1 d2
R * S = A B C D a1 a2 a3 b1 b3 b3 1 2 3 d2 d2 d2
R * S = A B C D a1 a2 b1 b2 1 2 d1 d2
R * S = A B C D a2 a3 b2 b3 2 3 d1 d2
What is the representation of the intersection?
R ∩ S = { t | t ∈ R and t ∈ S}
R ∩ S = { t | t ∈ R and t ∉ S}
R ∩ S = { t | t ∈ R or t ∈ S}
R ∩ S = { t | t has the form (a1, a2, …, an, b1, b2, …, bm) where {a1, a2, …, an} ∈ R; {b1, b2, …, bm} ∈ S }
Given two relations R and S as follows: R A B C a1 a1 a2 2 3 4 4 5 6 S A B C a1 a2 a3 3 4 1 6 6 7 What is the result of R ∪ S?
R ∪ S = A B C a1 a1 2 3 4 5
R ∪ S = A B C a1 a1 a2 a1 a3 2 3 4 3 1 4 5 6 6 7
R ∪ S = A B C a2 4 6
R ∪ S = A B C a1 a1 a2 a1 a3 2 3 4 3 1 4 5 6 6 7
Given relation R and attribute set X (with X = BC) R A B C a1 a2 a3 b1 b2 b3 c1 c2 c3 With the selection expression F:B = "b2", what is σF(R)?
σF(R) = A B C a2 b2 c2
σF(R) = A B C a1 b5 c1
σF(R) = A B C a3 b3 c3
σF(R) = A B C a1 b1 c1
Given relation R and attribute set X (with X = A) R A B C a1 a2 a1 b1 b2 b2 c1 c2 c1 What is the projection on attribute set X of relation R?
Πx R= A B a1 a2 a1 b1 b2 b2
Πx R= B C b1 b2 b2 c1 c2 c1
Πx R= A B C a1 a2 a1 b1 b2 b2 c1 c2 c1
Πx R= A a1 a2
Two relations R = {A1, A2, …, An} and S = {A'1, A'2, …, A'n} are called compatible relations if they satisfy
DOM(Ai) ⊃ DOM(A'i), for i = 1, …, n
DOM(Ai) ⊂ DOM(A'i), for i = 1, …, n
DOM(Ai) ≠ DOM(A'i), for i = 1, …, n
DOM(Ai) = DOM(A'i), for i = 1, …, n
What is the representation of the union?
R ∪ S = { t | t ∈ R and t ∈ S}
R ∪ S = { t | t ∈ R and t ∉ S}
R ∪ S = { t | t ∈ R or t ∈ S}
R ∪ S = { t | t
What is the representation of the union operation?
R ∪ S = { t | t ∈ R and t ∈ S}
R ∪ S = { t | t ∈ R and t ∉ S}
R ∪ S = { t | t ∈ R or t ∈ S}
R ∪ S = { t | t has the form (a1, a2, …, an, b1, b2, …, bm) where {a1, a2, …, an} ∈ R; {b1, b2, …, bm} ∈ S }
Given two relations R and S with the following forms: R and S, what is the result of R ∪ S?
R ∪ S = A B C a2 b2 c2
R ∪ S = A B C a1 b2 c2
R ∪ S = A B C a1 a2 b1 b2 c1 c2
R ∪ S = A B C a1 a1 a2 b1 b2 b2 c1 c2 c2
Write a relational algebra expression to find the names of companies supplying the item with code H2.
ΠMauSac='Vàng' (HANGHOA)
ΠMaCongTy(σMaHang='H2' CUNGCAP)
σMauSac='Vàng' (HANGHOA)
ΠTenCongTy * MaCongTy(σMaHang='H2' CUNGCAP * CONGTY) MaCongTy
What steps are included in the database design process?
Logical design, physical design
Requirements analysis, conceptual design, logical design, physical design
Requirements analysis, logical design
Physical design, requirements analysis
What step is called conceptual design?
Creating a conceptual schema for the database
Collecting data requirements
Physical design
Implementing the database
In the step of collecting and analyzing requirements, what does the database designer usually do?
Write source code for the database
Meet and interview users of the database
Design the internal structure of the database
Create access paths and organize the database files
When all requirements have been collected and analyzed, what is the next step?
Create a logical schema
Create a physical schema
Create a conceptual schema
Map the data model
What is the step to convert the conceptual schema from a high-level data model to an executable data model?
Design logical schema
Design physical level
Design physical level
Map data model
What is a collection of entities with the same attributes called?
Link type
Attribute set
Entity type
Link set
At which level is the entity-relationship model used to design the database?
Analysis
Conceptual
Logical
Physical
In an information management system about employees and departments, if each employee only works for one department, what is the degree of the relationship between EMPLOYEE and DEPARTMENT?
Degree 1
Degree 2
Degree 3
Degree 4
In a company, the entity type EMPLOYEE can be divided into smaller groups such as SECRETARY, ENGINEER, and TECHNICIAN. What are these groups called?
Parent class
Child class
Strong entity type
Weak entity type
When generalizing the entity types FAMILYCAR and TAXI into CAR, what does this mean?
FAMILYCAR and TAXI will lose their individual attributes
CAR will have the common attributes of both FAMILYCAR and TAXI
FAMILYCAR and TAXI no longer exist
CAR will not inherit any attributes from FAMILYCAR and TAXI
When converting a strong entity, if there are complex attributes, we only need to:
Keep the complex attribute
Ignore complex attributes
Take its simple component attributes
Only take key attributes
When converting the strong entity PRODUCT (ProductID, ProductName, Price, Color) to a relational model, which relation will we get?
PRODUCT (ProductID, ProductName, Color)
PRODUCT (ProductID, ProductName, Price, Color)
PRODUCT (ProductName, Price, Color)
PRODUCT (ProductID, Price)
For the ERD with entity types TEACHER (TeacherID, TeacherName) and CLASS (ClassID, ClassName), with n - n relationship TEACH. Which relational model is correct for converting the TEACH relationship?
Add TeacherID to CLASS
Add ClassID to TEACHER
Create relation TEACH (TeacherID, ClassID)
Create relation TEACH (TeacherID, ClassID, TeacherName)
Which relationship model is correct?
Add MaGV to LOPHOC
Add MaLH to GIANGVIEN
Create relationship DAY (MaGV, MaLH)
Create relationship DAY (MaGV, MaLH, TenGV)
What is the high-level conceptual data model used for?
To describe the technical details of the database
To communicate and confirm requirements with users
To define constraints and entity types
To optimize access paths
When converting weak entities, how will the primary key attributes of the parent entity type be included in relationship R?
As non-key attributes
As the primary key of R
As foreign keys of R
Must be included in R
What is an entity?
A characteristic of an object
An object or thing in the real world
A method of data storage
A relationship between entities
In database design, which step must indicate internal structures, access paths, and file organization for database files?
Logical schema design
Physical design
Conceptual design
Data model mapping
What is the final result in the requirement gathering and analysis step?
Conceptual schema
Execution schema
Set of user requirements
Data model
What is the attribute whose value is used to distinguish entities from each other called?
Foreign key attribute
Key attribute
Derived attribute
Complex attribute
Given the diagram as shown. When converting the QUANLY link to the relational model, which relationship is correct?
A. NHANVIEN (MaNV, NgaySinh, GioiTinh, Ten, DiaChi, MaDV)
B. NHANVIEN (MaNV, NgaySinh, GioiTinh, Ho, Ten, DiaChi, MaDV)
C. DONVI (MaDV, TenDV, DiaDiem, MaNV, NgayBatDau)
D. NHANVIEN (MaNV, NgaySinh, GioiTinh, Ten, DiaChi, MaDV)
Which of the following ER diagram representations is correct?
A.
B.
C.
D.
Which representation of the relationship is correct?
A.
B.
C.
D.
What is the level of the relationship between NHANVIEN, PHONGBAN, and DUAN?
Level 3
Level 4
Level 2
Level 1
What is SoGio in the relationship THAMGIA (MaNV, MaDa, SoGio)?
Primary key of NHANVIEN
Primary key of DUAN
Attribute of THAMGIA
Attribute of NHANVIEN
In the process of transformation, if the strong entity has a complex attribute 'DiaChi' with components 'SoNha', 'Duong', 'ThanhPho', what attributes will the relationship R have?
'DiaChi', 'SoNha'
'SoNha', 'Duong', 'ThanhPho'
'SoNha', 'DiaChi'
'DiaChi'
In the ER model, entities are represented by what shape?
Circle
Rectangle
Ellipse
Diamond
Why is the attribute MaNV2 added to the relationship CON (Ten, NgaySinh, GioiTinh, MaNV, MaNV2)?
Because MaNV2 is a complex attribute of the weak entity
Because MaNV2 is a foreign key referencing NHANVIEN and can be null
Because MaNV2 is the primary key of the strong entity
Because CON can have multiple primary key attributes.
Which representation of the entity type and its attributes is correct?
A.
B.
C.
D.
In the definition of functional dependency, if X → Y, what is true?
Y does not depend functionally on X
X and Y have the same value in all tuples of R
X and Y are always the same
X functionally determines Y
For the relation R(U) with U = {ABCD}, if A → BC and C → D, what is the result applying the accumulation axiom?
B → ACD
A → BCD
C → ABD
ABC → D
When we say Y is fully functionally dependent on X, what does this mean?
Only part of X is needed to determine Y
X cannot uniquely determine Y
Y cannot uniquely determine X
All attributes in X are necessary to determine Y
Which of the following functional dependencies is fully functional?
Student ID, Course ID -> Course Name, Credits
Student ID, Course ID -> Exam Score
Student ID, Class ID -> Student Name
Student ID, Course ID -> Student Name
What is the growth axiom in Armstrong's axioms?
If Y ⊆ X then X → Y
If X ⊆ Y then X → Y
If X → Y and Z ∈ U then XZ → YZ
If X → Y and Y → Z then X → Z
For the relation R(U) with U = {A -> B}, which axiom is applied to prove AC -> BC?
Transitive axiom
Accumulation axiom
Growth axiom
Given relation R(U) with U = {A -> B}. Which axiom can be applied to prove AC -> BC?
Transitive Axiom
Augmentation Axiom
Union Axiom
Reflexive Axiom
Given functional dependencies X -> Y, X -> Z. To prove X -> YZ, which axioms in Armstrong's axioms should be applied?
Reflexive and Growth
Growth and Transitive
Reflexive and Transitive
Augmentation
Given functional dependencies X -> Y, WY -> Z. To prove WX -> Z, which axioms in Armstrong's axioms should be applied?
Reflexive and Growth
Growth and Transitive
Reflexive and Transitive
Augmentation
Given r(U,F) with U = {ABCDE}; F = {AB -> C, DE -> B, C -> ABD, CD -> E}. Find the closure of the attribute set {BC}.
{BC}+ = {ABCDE}
{BC}+ = {AB}
{BC}+ = {CDE}
{BC}+ = {CABD}
Given r(U,F) with U={ABCDE}, F={AB→C, DE→B, C→ABD, CD→E}. Find the closure of the attribute set (CD)?
{CD}+ = {ABCDE}
{CD}+ = {ABD}
{CD}+ = {CDE}
{CD}+ = {AB}
Given r(U,F) with U = {ADIKL}; F = {K -> IL, A -> K, AK -> LD}. Find the closure of the attribute set {K}.
{K}+ = {IL}
{K}+ = {ADKL}
{K}+ = {KIL}
{K}+ = {K}
Given r(U,F) with U = {ADIKL}; F = {K -> IL, A -> K, AK -> LD}. Find the closure of the attribute set {L}.
{L}+ = ∅
{L}+ = {LD}
{L}+ = {L}
{L}+ = {IL}
What condition must a primary key in a table satisfy?
Can contain duplicate values
Can have NULL values
Must be a foreign key
Must have unique values and cannot be NULL
Given r(U,F) with U = {ABCD}; F = {A -> B, B -> C, D -> A}. What is the minimal key of this relation schema?
{ABD}
{CD}
{D}
{AB}
Given r(U,F) with U = {ABCDE}; F = {C -> AB, D -> C, CD -> EA}. What is the minimal key of this relation schema?
{C}
{AC}
{AD}
{D}
Given r(U,F) with U = {ABCDE}; F = {C -> AB, D -> C, CD -> EA}. In the algorithm to find all keys for r(U,F), which attribute set is the source set?
{CD}
{AC}
{D}
{C}
What is the source set for the relation r(U,F) with U = {ABCDE}; F = {AC -> D, A -> CB, AB -> ED}?
{CD}
{AC}
{D}
{C}
In the algorithm to find all keys for r(U,F), what is the intermediate attribute set for r(U,F) with U = {ABCDE}; F = {AC -> D, A -> CB, AB -> ED}?
{AB}
{BC}
{ED}
{CD}
What does the functional dependency f: X -> Y on relation R(U) mean?
Y determines X
X determines Y
Y is unrelated to X
X and Y have no relation
Which of the following is a full functional dependency?
Student ID, Course ID → Course Name, Credits
Student ID, Class ID → Student Name
Student ID, Course ID → Exam Score
Student ID, Course ID → Student Name
What is the correct statement of the reflexive axiom in Armstrong's axioms?
If X ⸦ Y then X → Y
If X → Y and Z ∈ U then XZ → YZ
If Y ⸦ X then X → Y
If X → Y and Y → Z then X → Z
For relation R(U) with U = {ABC} and F = {A → B}, which axiom is applied to prove AC → BC?
Reflexive axiom
Union axiom
Augmentation axiom
Transitive axiom
For r(U,F) with U = {ADIKL}; F = {K -> IL, A -> K, AK -> LD}. Find the closure of the attribute set {A}.
{A}+ = {ADKL}
{A}+ = {AK}
{A}+ = {ADIKL}
{A}+ = {K}
For r(U,F) with U = {ABCDE}; F = {BC -> CE, B -> A, AB -> ED}. What is the minimal key of this relation schema?
{AB}
{BC}
{B}
{AC}
For r(U,F) with U = {ABCD}; F = {A-> B, B -> C, CD -> A}. What is the minimal key of this relation schema?
{AD}
{B}
{A}
{CD}
For R(U), with U={ADIKL} and F={K→IL, A→K, AK→LD}. Find the closure of the attribute set {AD}?
{AD}+ = {ADK}
{AD}+ = {ADKL}
{AD}+ = {ADIKL}
{AD}+ = {IKL}
For r(U,F) with U = {ABCDE}; F = {AB -> C, DE -> B, C -> ABD, CD -> E}. Find the closure of the attribute set {AB}.
{AB}+ = {AB}
{AB}+ = {CABD}
{AB}+ = {ABCDE}
{AB}+ = {ABC}
Find the closure of the attribute set {AB}
{AB}
{CABD}
{ABCDE}
{ABC}
Given r(U,F) with U = {ABCD}; F = {A-> B, B -> C, A -> D}. Which dependency can be inferred from F?
B -> D
C -> BD
A -> C
A -> B
Assuming there are two functional dependency sets F and G defined on the attribute set U. F and G are considered equivalent if:
F and G have the same number of functional dependencies
F and G have the same attribute set
F+ = G+
F is a redundant cover of G
When is a functional dependency in set F considered redundant?
When that functional dependency cannot be removed from set F while preserving the meaning of F
When F removes that functional dependency while still being equivalent to F itself
When the right side of the functional dependency contains more than one attribute
When the left side of the functional dependency does not include all attributes of the attribute set U
What question does the membership problem pose?
Determine whether the functional dependency set F is empty or not
Check whether a functional dependency X → Y belongs to F+
Determine whether an attribute set U contains a certain attribute
Check whether a functional dependency set F is equivalent to G or not
When F is a cover of G, what does this mean?
F has more functional dependencies than G
F+ and G+ are equivalent
F is a subset of G
G does not contain any functional dependencies that are in F
In what case can a functional dependency set G not be considered a cover of F?
When G+ is not equivalent to F+
When G has the same number of functional dependencies as F
When G has fewer functional dependencies than F
When G and F contain the same functional dependencies
In the process of reducing the functional dependency set F to a minimal cover, if a functional dependency X → A is removed, what does this mean?
F+ does not change when X → A is removed
F+ changes when X → A is removed
X → A is an important functional dependency in F
X → A cannot be removed
What does it mean when the functional dependency X → A is removed?
F+ does not change when X → A is removed
F+ changes when X → A is removed
X → A is an important functional dependency in F
X → A cannot be removed from F
Given the set of functional dependencies F={A→B, B→C, A→C}. What should be done for F to be minimal?
Remove the functional dependency B→C from F
Remove the functional dependency A→C from F
Add the functional dependency AB→C to F
Keep the set F as it is
Given the set of functional dependencies F={A→B, AB→C, B→D}. What should be done for F to become minimal?
Remove the functional dependency AB→C
Add the functional dependency A→D to F
Remove the redundant attribute B on the left side of the functional dependency AB→C
Keep the set F as it is
In the set of functional dependencies F = { DE→A, A→B, AB→C, BD→B, BD→C}. Which functional dependency is redundant?
BD→B
A→B
BD→C
AB→C
In the set of functional dependencies F = { AD→B, B→E, AE→C, AE→E, BE→C }. Which functional dependency is redundant?
AE→C
BE→C
AE→E
There are no redundant functional dependencies
Given the relation DIEMTHI{MaSinhVien, MaMon, Diem} and F={ MaSinhVien, MaMon → Diem}. What is the highest normal form of the relation DIEMTHI?
1NF
2NF
BCNF
Does not meet any normal form
Given the schema r(U,F) with U={ABCDEL}; F={ AD→B, B→E, AE→CE, BE→C}. Normalize r(U,F) to 3NF, what sub-schemas will be obtained?
r1(ADB), r2(BEC), r3(AEC)
r1(ADL), r2(ADB), r3(BEC), r4(AEC)
r1(ADL), r2(BE), r3(AEC), r4(BEC)
r1(ADL), r2(ADB), r3(BE), r4(AEC), r5(BEC)
Given the schema r(U,F) with U={ABCDEL}; F={ED→C, C→B, BE→AB, BC→A}. Normalize r(U,F) to 3NF, what sub-schemas will be obtained?
r1(ACB), r2(BDE), r3(CDE)
r1(DEL), r2(EDC), r3(CBA), r4(BEA)
r1(DEL), r2(EDC
