Web Development Database Basics 3

Question 1

What is an index in a database used for?

Accepted Answer

To speed up data retrieval

Answer

An index is a data structure that improves the speed of data retrieval operations at the cost of additional storage and write overhead.

Question 2

Which SQL command is used to remove all rows from a table quickly without logging individual row deletions?

Accepted Answer

TRUNCATE

Answer

TRUNCATE removes all rows from a table much faster than DELETE because it doesn't log individual row deletions.

Question 3

In the context of databases, what is a 'view'?

Accepted Answer

A virtual table based on a stored query

Answer

A view is a virtual table defined by a stored SQL query; it doesn't store data itself but presents data from underlying tables.

Question 4

What does ACID stand for in database transactions?

Accepted Answer

Atomicity, Consistency, Isolation, Durability

Answer

ACID stands for Atomicity, Consistency, Isolation, and Durability — the four properties that guarantee reliable database transactions.

Question 5

Which SQL aggregate function returns the number of rows that match a condition?

Accepted Answer

COUNT()

Answer

COUNT() returns the number of rows that match the specified criteria in a query.

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