DAC DAC Database & SQL Analytics 2

Question 1

Which SQL window function assigns a unique sequential integer to rows within a partition ordered by a specified column?

Accepted Answer

ROW_NUMBER()

Answer

ROW_NUMBER() assigns a unique sequential number to each row within its partition, with no gaps or ties unlike RANK().

Question 2

What is a subquery in SQL?

Accepted Answer

A query nested inside another query

Answer

A subquery (or inner query) is a SELECT statement embedded within another SQL statement, used to produce intermediate results.

Question 3

Which normal form eliminates transitive dependencies in a relational database?

Accepted Answer

Third Normal Form (3NF)

Answer

Third Normal Form (3NF) requires that all non-key attributes depend only on the primary key and not on other non-key attributes (no transitive dependencies).

Question 4

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

Accepted Answer

To group rows sharing common values for use with aggregate functions

Answer

GROUP BY groups rows that have the same values in specified columns, enabling aggregate functions like SUM, COUNT, and AVG to be applied per group.

Question 5

In SQL, what does a FULL OUTER JOIN return?

Accepted Answer

All rows from both tables, with NULLs where there is no match on either side

Answer

A FULL OUTER JOIN returns all rows from both tables, pairing matching rows and filling in NULLs for rows in each table that have no match in the other.

Data Analytics Certifications (DAC) Practice Test

Data Analytics Certifications (DAC) Practice Test

DAC DAC Database & SQL Analytics 2