Web Development Database Basics 4

Question 1

What is the purpose of the GROUP BY clause in SQL?

Accepted Answer

To combine rows with the same value into summary rows

Answer

GROUP BY groups rows that share the same values in specified columns so aggregate functions can be applied to each group.

Question 2

Which NoSQL database type stores data as key-value pairs?

Accepted Answer

Key-value store

Answer

Key-value stores (like Redis) store data as pairs of unique keys and their associated values, optimized for fast lookups.

Question 3

What does 'atomicity' mean in a database transaction?

Accepted Answer

The transaction either completes fully or not at all

Answer

Atomicity guarantees that all operations within a transaction succeed together or are all rolled back if any step fails.

Question 4

What is a stored procedure in SQL?

Accepted Answer

A precompiled set of SQL statements stored and executed on the server

Answer

A stored procedure is a precompiled collection of SQL statements saved in the database that can be executed with a single call.

Question 5

Which SQL keyword eliminates duplicate rows from a result set?

Accepted Answer

DISTINCT

Answer

SELECT DISTINCT removes duplicate rows from query results, returning only unique value combinations.

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