Adam

“Getting a data science job would have been much harder without Dataquest. It’s a great product. I recommend it to anyone who asks me about how to get started.”

Adam Zabrodski

Data Science Manager @ Later

Course overview

A subquery is a query nested inside another query. Subqueries are useful to data practitioners for scaling and making more powerful queries. The main reason we have subqueries is the need to combine information from multiple tables. Information in a relational database isn’t stored in a single table; it’s shared between several tables.

In this course, you’ll learn various types of subqueries, how to use them, and why they are so valuable: scalar subquery, multi-rows subquery and multi-columns subquery. You’ll also learn how to write common table expressions in SQL.

Best of all, you’ll learn by doing — you’ll practice and get feedback directly in the browser.

Key skills

  • Nesting a query inside another query
  • Employing different types of subqueries
  • Employing common table expressions
  • Scaling your project with complex queries

Course outline

SQL Subqueries [6 lessons]

Scalar Subqueries in SQL 1h

Lesson Objectives
  • Extract a single value from a subquery
  • Employ a single value subquery in your queries
  • Identify why subqueries are useful

Multi-row and Multi-column Subqueries in SQL 1h

Lesson Objectives
  • Extract multiple rows from a subquery
  • Extract multiple columns from a subquery
  • Scale your project with multi-row subqueries

Nested and Correlated Subqueries in SQL 1h

Lesson Objectives
  • Nest a subquery inside another subquery
  • Write dependent subqueries
  • Write effective queries

Common Table Expression in SQL 1h

Lesson Objectives
  • Write Common Table Expressions (CTEs)
  • Write Recursive Common Table Expression

Views in SQL 1h

Lesson Objectives
  • Explain the concept and application of views in SQL
  • Create views
  • Query views
  • Create views from views
  • Drop views

The Dataquest guarantee

Guarantee

Dataquest has helped thousands of people start new careers in data. If you put in the work and follow our path, you’ll master data skills and grow your career.

Money

We believe so strongly in our paths that we offer a full satisfaction guarantee. If you complete a career path on Dataquest and aren’t satisfied with your outcome, we’ll give you a refund.

Master skills faster with Dataquest

Go from zero to job-ready

Go from zero to job-ready

Learn exactly what you need to achieve your goal. Don’t waste time on unrelated lessons.

Build your project portfolio

Build your project portfolio

Build confidence with our in-depth projects, and show off your data skills.

Challenge yourself with exercises

Challenge yourself with exercises

Work with real data from day one with interactive lessons and hands-on exercises.

Showcase your path certification

Showcase your path certification

Impress employers by completing a capstone project and certifying it with an expert review.

Grow your career with
Dataquest.

97%
of learners recommend
Dataquest for career advancement
4.9
Dataquest rating on
G2Crowd and SwitchUp
$30k
Average salary boost
for learners who complete a path
Aaron

Aaron Melton

Business Analyst at Aditi Consulting

“Dataquest starts at the most basic level, so a beginner can understand the concepts. I tried learning to code before, using Codecademy and Coursera. I struggled because I had no background in coding, and I was spending a lot of time Googling. Dataquest helped me actually learn.”

Jessi

Jessica Ko

Machine Learning Engineer at Twitter

“I liked the interactive environment on Dataquest. The material was clear and well organized. I spent more time practicing then watching videos and it made me want to keep learning.”

Victoria

Victoria E. Guzik

Associate Data Scientist at Callisto Media

“I really love learning on Dataquest. I looked into a couple of other options and I found that they were much too handhold-y and fill in the blank relative to Dataquest’s method. The projects on Dataquest were key to getting my job. I doubled my income!”

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