Data Warehousing on AWS Training Data Warehousing on AWS: SQL 4

Question 1

Which Redshift SQL feature allows you to query data stored in Amazon S3 without loading it into Redshift tables?

Accepted Answer

Redshift Spectrum

Answer

Redshift Spectrum enables SQL queries directly against data in S3 using external tables defined in an external schema.

Question 2

In Redshift SQL, what does the NVL function do?

Accepted Answer

Returns the first non-NULL expression from its arguments

Answer

NVL(expr1, expr2) returns expr1 if it is not NULL; otherwise it returns expr2, equivalent to COALESCE with two arguments.

Question 3

Which SQL construct in Redshift lets you define a reusable named subquery within a single SQL statement?

Accepted Answer

Common Table Expression (WITH clause)

Answer

A Common Table Expression (CTE) using the WITH clause defines a named, reusable subquery scoped to a single SQL statement.

Question 4

What is the result of performing integer division in Redshift SQL, e.g., SELECT 7 / 2?

Accepted Answer

3

Answer

Redshift follows standard SQL integer division rules: dividing two integers truncates the decimal, so 7 / 2 = 3.

Question 5

In Redshift, which function converts a string to lowercase?

Accepted Answer

LOWER()

Answer

LOWER() is the standard SQL function in Redshift that converts all characters in a string to lowercase.

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