Functional dependency definition in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to define functional dependency: In a relation, attribute B is functionally dependent on attribute A if each value of A is associated with exactly {{BLANK_1}} value of B.

DBMS Theory

In a relation, attribute B is functionally dependent on attribute A if each value of A is associated with exactly [1] value of B.

Drag options to blanks, or click blank then click option'

Amultiple

Bmany

Czero

Done

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'many' or 'multiple' which implies multiple B values for one A.

Functional dependency means for each value of attribute A, there is exactly one corresponding value of attribute B.

2fill in blank

medium

Complete the statement: If attribute A functionally determines attribute B, it is denoted as A {{BLANK_1}} B.

DBMS Theory

If attribute A functionally determines attribute B, it is denoted as A [1] B.

Drag options to blanks, or click blank then click option'

A=

B<-

C->

D=>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<-' or '=' which are incorrect notations for functional dependency.

The notation for functional dependency is A -> B, meaning A determines B.

3fill in blank

hard

Fix the error in this definition: 'A functional dependency A {{BLANK_1}} B means B uniquely determines A.'

DBMS Theory

A functional dependency A [1] B means B uniquely determines A.

Drag options to blanks, or click blank then click option'

A<-

B=

C->

D=>

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the direction of functional dependency arrows.

The statement is reversed. If B uniquely determines A, the correct notation is B -> A, so A <- B.

4fill in blank

hard

Fill both blanks to complete the functional dependency definition: Attribute B is functionally dependent on attribute A if for every {{BLANK_1}} of A, there is exactly {{BLANK_2}} value of B.

DBMS Theory

Attribute B is functionally dependent on attribute A if for every [1] of A, there is exactly [2] value of B.

Drag options to blanks, or click blank then click option'

Avalue

Bmany

Cone

Dattribute

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'attribute' instead of 'value' for the first blank.

Functional dependency means for every value of A, there is exactly one value of B.

5fill in blank

hard

Fill all three blanks to complete the functional dependency notation: If {{BLANK_1}} functionally determines {{BLANK_2}}, it is written as {{BLANK_3}}.

DBMS Theory

If [1] functionally determines [2], it is written as [3].

Drag options to blanks, or click blank then click option'

Aattribute A

Battribute B

CA -> B

DB -> A

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the attributes or the arrow direction in the notation.

The correct notation is: If attribute A functionally determines attribute B, it is written as A -> B.

Practice

1. What does the functional dependency X -> Y mean in a database?

easy

A. Knowing X allows you to find Y uniquely

B. X and Y are unrelated data sets

C. Y determines X uniquely

D. X and Y are always equal

Solution

1. Step 1: Understand the notation X -> Y

   This notation means that the value of X determines the value of Y uniquely in the database.

2. Step 2: Interpret the meaning in simple terms

   If you know X, you can find Y without ambiguity. This is the core idea of functional dependency.

3. Final Answer:

   Knowing X allows you to find Y uniquely -> Option A

4. Quick Check:

   Functional dependency means X determines Y [OK]

Hint: Remember: X determines Y means knowing X gives Y [OK]

Common Mistakes:

• Confusing which attribute determines which
• Thinking X and Y are unrelated
• Assuming dependency means equality

2. Which of the following is the correct way to write a functional dependency?

easy

A. X -> Y

B. X = Y

C. X <-> Y

D. X + Y

Solution

1. Step 1: Recall the standard notation for functional dependency

   The correct notation uses an arrow pointing from X to Y, written as X -> Y.

2. Step 2: Eliminate incorrect options

   X = Y means equality, X <-> Y suggests bidirectional dependency, and X + Y is not a valid notation here.

3. Final Answer:

   X -> Y -> Option A

4. Quick Check:

   Functional dependency uses arrow notation [OK]

Hint: Look for arrow notation X -> Y for functional dependency [OK]

Common Mistakes:

• Using equals sign instead of arrow
• Confusing bidirectional with functional dependency
• Using plus sign mistakenly

3. Given a table with columns StudentID and StudentName, which functional dependency is correct?

medium

A. StudentName -> StudentID

B. StudentID -> StudentName

C. StudentID -> StudentID

D. StudentName -> StudentName

Solution

1. Step 1: Identify the unique identifier

   Usually, StudentID uniquely identifies a student, so it determines StudentName.

2. Step 2: Check the direction of dependency

   Knowing StudentID gives StudentName, but not necessarily the other way around.

3. Final Answer:

   StudentID -> StudentName -> Option B

4. Quick Check:

   Unique ID determines name [OK]

Hint: Unique keys determine other attributes [OK]

Common Mistakes:

• Assuming name uniquely identifies ID
• Confusing attribute roles
• Ignoring uniqueness of StudentID

4. Identify the error in this functional dependency statement: EmployeeName -> EmployeeID where EmployeeID is unique.

medium

A. EmployeeName must be numeric

B. EmployeeID cannot be unique

C. Functional dependency must be bidirectional

D. EmployeeName may not uniquely determine EmployeeID

Solution

1. Step 1: Understand uniqueness of EmployeeID

   EmployeeID is unique, so it can determine EmployeeName, but not vice versa.

2. Step 2: Analyze the given dependency

   EmployeeName may repeat for different employees, so it cannot uniquely determine EmployeeID.

3. Final Answer:

   EmployeeName may not uniquely determine EmployeeID -> Option D

4. Quick Check:

   Non-unique attribute cannot determine unique ID [OK]

Hint: Only unique attributes determine others [OK]

Common Mistakes:

• Assuming all attributes are unique
• Thinking dependency is always two-way
• Confusing attribute types

5. In a database, if A -> B and B -> C, what can we conclude about the functional dependency between A and C?

hard

A. B -> A

B. C -> A

C. A -> C

D. C -> B

Solution

1. Step 1: Understand transitive dependency

   If A determines B, and B determines C, then A determines C by transitivity.

2. Step 2: Apply the rule to given dependencies

   Since A -> B and B -> C, it follows that A -> C.

3. Final Answer:

   A -> C -> Option C

4. Quick Check:

   Functional dependencies are transitive [OK]

Hint: Chain dependencies to find indirect ones [OK]

Common Mistakes:

• Reversing dependency direction
• Ignoring transitive property
• Confusing attributes order