Relational & NoSQL Database Design Flashcards

Which normal form eliminates transitive dependencies among non-key attributes?

Answer: Third Normal Form (3NF)

3NF removes transitive dependencies where a non-key column depends on another non-key column rather than directly on the primary key.

In a relational schema, a foreign key constraint ensures which property?

Answer: Referential integrity

A foreign key constraint enforces referential integrity by ensuring that a value in one table corresponds to an existing value in the referenced table.

Which NoSQL data model stores data as key-value pairs with no fixed schema?

Answer: Key-value store

Key-value stores use a simple hash-map structure where each unique key maps to a value, requiring no predefined schema.

What does the CAP theorem state about distributed databases?

Answer: A system can guarantee at most two of Consistency, Availability, and Partition tolerance

The CAP theorem states that a distributed system can only guarantee two of the three properties: Consistency, Availability, and Partition tolerance.

Which join type returns all rows from both tables, filling NULL where no match exists?

Answer: FULL OUTER JOIN

A FULL OUTER JOIN returns all rows from both tables, placing NULL in columns where a matching row from the other table does not exist.

In MongoDB, which operation is used to update only specific fields in a document without replacing the entire document?

Answer: updateOne() with $set

updateOne() with the $set operator modifies only the specified fields of a document, leaving the rest of the document unchanged.

Which property of relational databases ensures that a committed transaction remains persistent even after a system failure?

Answer: Durability

Durability, the 'D' in ACID, guarantees that once a transaction is committed, its effects are permanently recorded even in the event of a crash.