Data and Analytics SQL and Database Fundamentals 2

Question 1

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

Accepted Answer

COUNT()

Answer

COUNT() returns the number of rows that match the specified condition, or total rows when used with *.

Question 2

What is a foreign key in a relational database?

Accepted Answer

A column that references the primary key of another table

Answer

A foreign key establishes a referential link between a column in one table and the primary key of another table.

Question 3

What SQL statement is used to retrieve data from a database?

Accepted Answer

SELECT

Answer

SELECT is the SQL DML statement used to query and retrieve data from one or more database tables.

Question 4

Which SQL window function assigns a unique rank to each row within a partition?

Accepted Answer

ROW_NUMBER()

Answer

ROW_NUMBER() assigns a unique sequential integer to each row within a partition, with no gaps or ties.

Question 5

What does a NULL value represent in a database?

Accepted Answer

An unknown or missing value

Answer

NULL represents the absence of a value or an unknown value in a database field.

Data and Analytics Practice Test