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DBMS Keys Multiple-Choice Questions (MCQs)
DBMS Keys MCQs: This section contains DBMS Keys Multiple-Choice Questions (MCQs) and Answers.
Submitted by Anushree Goswami, on February 03, 2022
1. What is TRUE about Keys?
- Relational databases rely heavily on keys
- Any row or record in the table can be uniquely identified with this field
- Relationships between tables can also be established using it
- All of the above
Answer: D) All of the above
Explanation:
In case of Keys -
- Relational databases rely heavily on keys
- Any row or record in the table can be uniquely identified with this field
- Relationships between tables can also be established using it
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2. How many types of keys are there?
- 1
- 2
- 3
- 4
Answer: D) 4
Explanation:
There are 4 types of keys: Primary Key, Super Key, Candidate Key, Foreign Key.
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3. What is TRUE about Primary Key?
- An entity can only be uniquely identified by using the first key
- From these lists, the most appropriate key becomes a primary key
- Primary keys are selected for each entity according to its requirements and developers
- All of the above
Answer: d) All of the above
Explanation:
In case of Primary Key -
- An entity can only be uniquely identified by using the first key
- From these lists, the most appropriate key becomes a primary key
- Primary keys are selected for each entity according to its requirements and developers
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4. Tuples can be uniquely identified by an attribute or set of attributes known as a ___ key.
- Primary
- Foreign
- Candidate
- Composite
Answer: C) Candidate
Explanation:
Tuples can be uniquely identified by an attribute or set of attributes known as a candidate key.
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5. What is TRUE about the Candidate key?
- Candidate keys are considered for all attributes except the primary key
- Both the candidate keys and the primary key are equally strong
- Both A and B
- None of the above
Answer: C) Both A and B
Explanation:
In case of Candidate Key -
- Candidate keys are considered for all attributes except the primary key
- Both the candidate keys and the primary key are equally strong
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6. Tuples are uniquely identified by a ___ key, which is a set of attributes.
- Primary
- Candidate
- Super
- Alternate
Answer: C) Super
Explanation:
Tuples are uniquely identified by a super key, which is a set of attributes.
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7. Which of the following statements is TRUE?
- Candidate keys are subsets of super keys
- Candidate keys are supersets of super keys
- Candidate keys are sets of super keys
- Candidate keys are super keys
Answer: B) Candidate keys are supersets of super keys
Explanation:
Candidate keys are subsets of super keys.
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8. Which of the following is TRUE about foreign keys?
- Tables that contain foreign keys contain columns that point to another table's primary key
- Primary key of one table could be the foreign key for another table
- Both A and B
- None of the above
Answer: C) Both A and B
Explanation:
In case of foreign keys -
- Tables that contain foreign keys contain columns that point to another table's primary key
- Primary key of one table could be the foreign key for another table
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9. Which of the following statements is TRUE?
- Both the candidate keys and the primary key are equally strong
- Both the candidate keys and the primary key are equally weak
- Candidate key is weaker than the Primary Key
- Primary key is weaker than the Candidate key
Answer: A) Both the candidate keys and the primary key are equally strong
Explanation:
Both the candidate keys and the primary key are equally strong.
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10. Which of the following key is considered unique in a table?
- Primary key
- Candidate key
- Foreign key
- Super key
Answer: A) Primary key
Explanation:
Primary key is considered unique in a table.
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