A 10 10 11 12 13 14 B C B1 C1 B2 C2 B4 C1 B3 C4 B1 C1 #5 B3 C4 #6 Tuple# #1 #2 #3 #4 . Which of the following dependencies may hold in the above relation? If the dependency cannot hold, explain why by specifying the tuples that causes th violation? į. A⇒B ii. B⇒C iii. C⇒B iv. B⇒A v. C⇒A . Does the above relation have a potential candidate key? Explain.

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
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Chapter1: Introduction
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So I am currently learning functional dependencies and need help with this HW question......

### Database Relation and Functional Dependencies

#### Table Structure

| A  | B  | C  | Tuple# |
|----|----|----|--------|
| 10 | B1 | C1 | #1     |
| 10 | B2 | C2 | #2     |
| 11 | B4 | C1 | #3     |
| 12 | B3 | C4 | #4     |
| 13 | B1 | C1 | #5     |
| 14 | B3 | C4 | #6     |

#### Questions

**a. Which of the following dependencies may hold in the above relation? If the dependency cannot hold, explain why by specifying the tuples that cause the violation.**

i. \( A \rightarrow B \)  
ii. \( B \rightarrow C \)  
iii. \( C \rightarrow B \)  
iv. \( B \rightarrow A \)  
v. \( C \rightarrow A \)  

**b. Does the above relation have a potential candidate key? Explain.**

---

In analyzing functional dependencies:

- **\( A \rightarrow B \)**: Check if the same value of A maps to a unique value of B. For tuples #1 and #2 with A=10, B is different (B1, B2), causing a violation.
  
- **\( B \rightarrow C \)**: Check if the same value of B maps to a unique value of C. There are no repetitions of B-values that map to different C-values, thus it may hold.
  
- **\( C \rightarrow B \)**: Check if the same value of C maps to a unique value of B. For tuples #1 and #3 with C=C1, B is different (B1, B4), causing a violation.
  
- **\( B \rightarrow A \)**: Check if the same value of B maps to a unique value of A. Multiple examples such as tuples #1 and #5 (B1 to A=10, 13) show violations.
  
- **\( C \rightarrow A \)**: Check if the same value of C maps to a unique value of A. For tuples #1 and #3 with C=C1, A is different (10, 11), causing a violation.

**Candidate Key Analysis**

A candidate key should uniquely identify all tuples in the relation. Here, no single attribute is able to uniquely
Transcribed Image Text:### Database Relation and Functional Dependencies #### Table Structure | A | B | C | Tuple# | |----|----|----|--------| | 10 | B1 | C1 | #1 | | 10 | B2 | C2 | #2 | | 11 | B4 | C1 | #3 | | 12 | B3 | C4 | #4 | | 13 | B1 | C1 | #5 | | 14 | B3 | C4 | #6 | #### Questions **a. Which of the following dependencies may hold in the above relation? If the dependency cannot hold, explain why by specifying the tuples that cause the violation.** i. \( A \rightarrow B \) ii. \( B \rightarrow C \) iii. \( C \rightarrow B \) iv. \( B \rightarrow A \) v. \( C \rightarrow A \) **b. Does the above relation have a potential candidate key? Explain.** --- In analyzing functional dependencies: - **\( A \rightarrow B \)**: Check if the same value of A maps to a unique value of B. For tuples #1 and #2 with A=10, B is different (B1, B2), causing a violation. - **\( B \rightarrow C \)**: Check if the same value of B maps to a unique value of C. There are no repetitions of B-values that map to different C-values, thus it may hold. - **\( C \rightarrow B \)**: Check if the same value of C maps to a unique value of B. For tuples #1 and #3 with C=C1, B is different (B1, B4), causing a violation. - **\( B \rightarrow A \)**: Check if the same value of B maps to a unique value of A. Multiple examples such as tuples #1 and #5 (B1 to A=10, 13) show violations. - **\( C \rightarrow A \)**: Check if the same value of C maps to a unique value of A. For tuples #1 and #3 with C=C1, A is different (10, 11), causing a violation. **Candidate Key Analysis** A candidate key should uniquely identify all tuples in the relation. Here, no single attribute is able to uniquely
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