Understanding Primary Keys in Databases

What is a primary key in a database?

• A primary key is an optional field in a database.

• A primary key is a type of foreign key.

• A primary key can be duplicated across records.

• A primary key is a unique identifier for a record in a database.

Why is a primary key important for a database?

• A primary key is only necessary for relational databases, not for others.

• A primary key can be duplicated across records to allow for flexibility.

• A primary key is important because it ensures each record is unique and maintains data integrity.

• A primary key is used to store large amounts of data efficiently.

Can a primary key contain NULL values?

• A primary key can contain multiple NULL values.

• Yes, a primary key can contain NULL values.

• No, a primary key cannot contain NULL values.

• A primary key can have one NULL value.

What is the difference between a primary key and a foreign key?

• A primary key can be null; a foreign key cannot be null.

• A primary key is used for indexing; a foreign key is for data validation.

• A primary key uniquely identifies records; a foreign key links records between tables.

• A primary key is always a string; a foreign key is always an integer.

How many primary keys can a table have?

• 3

• Unlimited

• 1

• 2

What happens if you try to insert a duplicate primary key?

• The duplicate key will be automatically updated.

• The database will ignore the duplicate key and proceed.

• The insertion will succeed without any issues.

• The insertion will fail with an error.

Which data types are commonly used for primary keys?

• Float

• Boolean

• Integer, String (UUID), Composite Key

• DateTime

Can a composite key be used as a primary key?

• A composite key is only used for foreign keys.

• No, a composite key cannot be used as a primary key.

• Yes, a composite key can be used as a primary key.

• Composite keys are not allowed in any database.

What is the role of a primary key in ensuring data integrity?

• The primary key ensures data integrity by uniquely identifying records and preventing duplicates.

• The primary key is used to encrypt sensitive data in the database.

• The primary key allows multiple records to have the same identifier.

• The primary key serves as a foreign key in other tables.

How do you define a primary key in SQL?

• A primary key is automatically created for every table in SQL.

• A primary key can be any column in a table without restrictions.

• A primary key is defined using the PRIMARY KEY constraint in SQL.

• A primary key is defined using the UNIQUE constraint in SQL.