Master SQL for Data Analysis - Conditional Logic – Single Row

The video tutorial explains the concept of subqueries in SQL, focusing on their use in filtering data within the WHERE clause. It provides examples of using subqueries to find products with weights greater than the average and those with the maximum price. The tutorial also covers best practices for writing subqueries, such as ensuring they return a single value when using aggregate functions and placing them on the right side of comparison operators. It emphasizes the importance of testing subqueries separately before integrating them into larger queries.

What is the primary purpose of a subquery in SQL?

• To delete data from a table

• To filter data within the WHERE clause

• To create a new table

• To update data in a table

In the example of finding products with weight greater than the average, what is the main advantage of combining queries?

• It reduces the number of tables needed

• It allows for manual calculation of averages

• It increases the complexity of the query

• It automates the filtering process

Which of the following is a requirement for a subquery in SQL?

• It must use an alias

• It must be enclosed in parentheses

• It must include an ORDER BY clause

• It must return multiple rows

Why is it important for a subquery to return a single value when used with certain operators?

• To increase query execution time

• To allow for multiple comparisons

• To enable the use of ORDER BY

• To ensure compatibility with the main query

What is the role of aggregate functions in subqueries?

• They ensure the subquery returns multiple values

• They allow the subquery to return a single value

• They are used to sort the results

• They are required for all subqueries

What is a key consideration when using a subquery in an equal comparison?

• The subquery must return multiple columns

• The subquery must include an alias

• The subquery must use a different table

• The subquery must return a single row

In the example of finding products with the maximum price, what SQL function is used in the subquery?

• SUM

• MIN

• COUNT

• MAX