Database Management Concepts Flashcards

What is a deadlock in database management?

Answer: A situation where two transactions wait indefinitely for each other's locked resources

A deadlock occurs when two or more transactions each hold locks the others need, causing all to wait forever.

Which database model stores data as collections of key-value pairs, documents, or graphs?

Answer: NoSQL database

NoSQL databases use non-tabular storage models such as key-value, document, column-family, or graph formats.

What does the SQL keyword DISTINCT do in a SELECT statement?

Answer: Returns only unique values, eliminating duplicates

DISTINCT ensures only unique rows are returned by removing duplicate values from query results.

In a database context, what is a view?

Answer: A virtual table based on the result of a SQL query

A view is a stored SQL query that presents data from one or more tables as if it were a single virtual table.

Which concurrency control technique uses timestamps to order transactions?

Answer: Timestamp-based protocol

The timestamp-based protocol assigns timestamps to transactions and uses them to determine the serialization order.

What is data redundancy in a database?

Answer: Storing the same data in multiple places unnecessarily

Data redundancy occurs when the same data is stored in more than one place, wasting storage and risking inconsistencies.

Which SQL aggregate function returns the total number of rows in a result set?

Answer: COUNT()

COUNT() returns the number of rows that match a specified condition or all rows in a table.