Microsoft SQL Server Development for Everyone - SQL AVG Aggregate Function

This video tutorial covers the use of the AVG aggregate function in SQL, focusing on calculating average grades. It begins with a database structure change to accommodate numerical grades, followed by a detailed explanation of handling design changes safely. The tutorial then demonstrates how to use aggregate functions and SQL queries to calculate averages, including filtering and ordering results. Key concepts such as the use of the GROUP BY clause and handling NULL values are also discussed.

What is the primary reason for changing the database structure from letter grades to numerical grades?

• To improve data security

• To reduce storage space

• To allow for mathematical operations like averaging

• To make it easier to read

What potential issue might arise when changing a column from a string to a float?

• The data might become unreadable

• The data might get corrupted

• The data might be duplicated

• The data might be deleted

What should you do if you encounter an error preventing you from saving changes that require table recreation?

• Restart the database

• Contact technical support

• Untick the option in the database designer settings

• Reinstall the database software

Why is it important to ensure that the numerical values entered are not IDs when calculating averages?

• IDs are not unique

• Averaging IDs would not provide meaningful information

• IDs are too large to average

• IDs are not numerical

What SQL clause is used to filter records for a specific course ID?

• GROUP BY

• ORDER BY

• HAVING

• WHERE

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

• To delete duplicate rows

• To sort the data

• To filter the data

• To group rows that have the same values in specified columns

Which function is used to calculate the average of a column in SQL?

• SUM

• MAX

• COUNT

• AVG

What SQL clause should be used to filter results based on an aggregated column?

• HAVING

• ORDER BY

• WHERE

• GROUP BY

How can you order the results by the average grade in SQL?

• Using WHERE AVG(grade)

• Using ORDER BY AVG(grade)

• Using GROUP BY AVG(grade)

• Using HAVING AVG(grade)

What is the correct way to filter out null values in an aggregated column?

• ORDER BY AVG(grade) IS NULL

• WHERE AVG(grade) IS NULL

• HAVING AVG(grade) IS NOT NULL

• GROUP BY AVG(grade) IS NOT NULL