MySQL - Primary Keys and Indexes MCQ

MySQL – Primary Keys and Indexes MCQ

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1. What is the primary purpose of a primary key in MySQL?

To enforce data uniqueness

To speed up SELECT queries

To store binary data

To allow NULL values in a column

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2. Which attribute must a primary key column NOT have in MySQL?

Non-nullability

Nullable

Fast Retrieval

Uniqueness

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3. What is the primary function of an index in a MySQL table?

To ensure column uniqueness

To allow NULL values in a column

To optimize data retrieval

To store binary data

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4. Which type of index does MySQL create automatically when you define a primary key?

Non-unique index

Non-null index

Composite index

Unique index

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5. In MySQL, what does a UNIQUE constraint on a column ensure?

Non-nullable column

Fast data retrieval

Duplicate values

Composite primary key

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6. How does an index speed up data retrieval in MySQL?

By enforcing data uniqueness

By optimizing data storage

By allowing NULL values in a column

By providing direct access to rows

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7. What happens when you create a foreign key constraint in MySQL?

The foreign key column stores binary data

An index is created on the foreign key column

The foreign key column becomes the primary key

The foreign key column allows NULL values

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8. Which type of index is automatically created when you define a primary key in MySQL?

Unique index

Non-null index

Composite index

Non-unique index

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9. What is the primary benefit of using a primary key in MySQL?

Allowing NULL values in a column

Enforcing data type constraints

Ensuring data uniqueness

Storing binary data

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10. What is the main purpose of a foreign key in MySQL?

To establish relationships between tables

To enforce data type constraints

To create indexes for queries

To optimize data retrieval

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11. What is a composite primary key in MySQL?

A primary key that is automatically generated

A primary key that consists of multiple columns

A primary key that allows NULL values

A primary key that enforces data uniqueness

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12. Which type of index is automatically created on a foreign key column in MySQL?

Non-null index

Unique index

Composite index

Non-unique index

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13. How does an index affect the performance of SELECT queries in MySQL?

Causes query errors

Slows down query performance

Speeds up query performance

Has no impact on query performance

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14. What is a recommended practice when choosing columns for indexing in MySQL?

Index all columns in the table

Index columns frequently used in queries

Index only columns with few unique values

Index columns that are never used

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15. Which attribute should NOT be associated with a primary key column in MySQL?

Non-nullability

Uniqueness

Fast data retrieval

Nullable

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16. What happens when you create a UNIQUE constraint on a column in MySQL?

The column enforces data uniqueness

The column becomes a primary key

The column stores binary data

The column allows NULL values

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17. In MySQL, what is the primary function of a primary key?

To enforce data uniqueness

To allow NULL values in a column

To store binary data

To optimize data retrieval

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18. What type of index is created when you define a primary key in MySQL?

Non-unique index

Unique index

Non-null index

Composite index

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19. What is the primary purpose of using a UNIQUE constraint in MySQL?

Allowing NULL values in a column

Ensuring data uniqueness

Optimizing data retrieval

Enforcing data type constraints

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20. How does a primary key affect data integrity in MySQL?

It allows NULL values in a column

It stores binary data

It enforces data type constraints

It prevents data duplication

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21. What is the primary benefit of using indexes in a MySQL table?

Slowing down data retrieval

Allowing NULL values in a column

Optimizing data retrieval

Ensuring data uniqueness

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22. When defining a primary key in MySQL, what is recommended for the selection of columns?

Select columns with frequent data changes

Opt for columns that frequently appear in queries

Choose columns with no unique values

Avoid columns used in WHERE clauses

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23. Which attribute of a primary key column ensures data uniqueness in MySQL?

Composite key

Uniqueness

Non-nullability

NULL values allowed

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24. How can you create a composite primary key in MySQL?

By specifying multiple columns separated by commas

By selecting a non-null column

By defining a UNIQUE constraint

By using the AUTO_INCREMENT attribute

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25. What type of queries are typically optimized by using indexes in MySQL?

UPDATE queries

SELECT queries

DELETE queries

INSERT queries

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26. Which attribute should NOT be associated with an indexed column in MySQL?

Uniqueness

Non-nullability

Fast data retrieval

Nullable

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27. What is the primary purpose of creating a foreign key constraint in MySQL?

To optimize data retrieval

To establish relationships between tables

To enforce data uniqueness

To create indexes for queries

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