SELECT with WHERE, ORDER BY, GROUP BY in DBMS Theory - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the WHERE clause do in a SELECT statement?

The WHERE clause filters rows to include only those that meet a specified condition.

beginner

How does the ORDER BY clause affect the result of a SELECT query?

The ORDER BY clause sorts the result rows by one or more columns, either ascending or descending.

intermediate

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

The GROUP BY clause groups rows that have the same values in specified columns, often used with aggregate functions like COUNT or SUM.

intermediate

Can you use WHERE and GROUP BY together? If yes, in what order?

Yes, you use WHERE first to filter rows, then GROUP BY to group the filtered rows.

intermediate

What happens if you use ORDER BY after GROUP BY?

The query first groups rows, then sorts the grouped results according to the ORDER BY clause.

Which clause filters rows before grouping in a SELECT query?

A GROUP BY

B ORDER BY

C WHERE

D HAVING

The WHERE clause filters rows before grouping. HAVING filters after grouping.

What does ORDER BY column_name DESC do?

A Sorts rows by column_name in descending order

B Filters rows where column_name is DESC

C Groups rows by column_name

D Sorts rows by column_name in ascending order

DESC means descending order, so rows are sorted from highest to lowest.

Which clause is used to group rows with the same value in a column?

A WHERE

B GROUP BY

C ORDER BY

D SELECT

GROUP BY groups rows that share the same value in specified columns.

If you want to filter groups after grouping, which clause do you use?

A HAVING

B ORDER BY

C GROUP BY

D WHERE

HAVING filters groups after GROUP BY has been applied.

In which order are these clauses processed in a query: WHERE, GROUP BY, ORDER BY?

A ORDER BY, WHERE, GROUP BY

B GROUP BY, ORDER BY, WHERE

C GROUP BY, WHERE, ORDER BY

D WHERE, GROUP BY, ORDER BY

First WHERE filters rows, then GROUP BY groups them, then ORDER BY sorts the result.

Explain how the WHERE, GROUP BY, and ORDER BY clauses work together in a SELECT query.

Think about the order SQL processes these clauses.

Describe a real-life example where you would use WHERE, GROUP BY, and ORDER BY in a database query.

Imagine you want to see total sales per region, only for recent months, sorted by highest sales.