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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?

  1. Relational databases rely heavily on keys
  2. Any row or record in the table can be uniquely identified with this field
  3. Relationships between tables can also be established using it
  4. All of the above

Answer: D) All of the above

Explanation:

In case of Keys -

  1. Relational databases rely heavily on keys
  2. Any row or record in the table can be uniquely identified with this field
  3. Relationships between tables can also be established using it

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2. How many types of keys are there?

  1. 1
  2. 2
  3. 3
  4. 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?

  1. An entity can only be uniquely identified by using the first key
  2. From these lists, the most appropriate key becomes a primary key
  3. Primary keys are selected for each entity according to its requirements and developers
  4. All of the above

Answer: d) All of the above

Explanation:

In case of Primary Key -

  1. An entity can only be uniquely identified by using the first key
  2. From these lists, the most appropriate key becomes a primary key
  3. 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.

  1. Primary
  2. Foreign
  3. Candidate
  4. 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?

  1. Candidate keys are considered for all attributes except the primary key
  2. Both the candidate keys and the primary key are equally strong
  3. Both A and B
  4. None of the above

Answer: C) Both A and B

Explanation:

In case of Candidate Key -

  1. Candidate keys are considered for all attributes except the primary key
  2. 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.

  1. Primary
  2. Candidate
  3. Super
  4. 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?

  1. Candidate keys are subsets of super keys
  2. Candidate keys are supersets of super keys
  3. Candidate keys are sets of super keys
  4. 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?

  1. Tables that contain foreign keys contain columns that point to another table's primary key
  2. Primary key of one table could be the foreign key for another table
  3. Both A and B
  4. None of the above

Answer: C) Both A and B

Explanation:

In case of foreign keys -

  1. Tables that contain foreign keys contain columns that point to another table's primary key
  2. 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?

  1. Both the candidate keys and the primary key are equally strong
  2. Both the candidate keys and the primary key are equally weak
  3. Candidate key is weaker than the Primary Key
  4. 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?

  1. Primary key
  2. Candidate key
  3. Foreign key
  4. Super key

Answer: A) Primary key

Explanation:

Primary key is considered unique in a table.

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