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Joining Data in SQL

Join two or three tables together into one, combine tables using set theory, and work with subqueries in PostgreSQL.

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5 Hours13 Videos53 Exercises305,686 Learners4400 XPData Analyst TrackData Analyst TrackSQL Fundamentals TrackSQL Server Fundamentals Track

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Course Description

Now that you've learned the basics of SQL in our Introduction to SQL course, it's time to supercharge your queries using joins and relational set theory. In this course, you'll learn all about the power of joining tables while exploring interesting features of countries and their cities throughout the world. You will master inner and outer joins, as well as self joins, semi joins, anti joins and cross joins—fundamental tools in any PostgreSQL wizard's toolbox. Never fear set theory again after learning all about unions, intersections, and except clauses through easy-to-understand diagrams and examples. Lastly, you'll be introduced to the challenging topic of subqueries. You will be able to visually grasp these ideas by using Venn diagrams and other linking illustrations.

  1. 1

    Introduction to joins


    In this chapter, you'll be introduced to the concept of joining tables, and will explore the different ways you can enrich your queries using inner joins and self joins. You'll also see how to use the case statement to split up a field into different categories.

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    Introduction to INNER JOIN
    50 xp
    Inner join
    100 xp
    Inner join (2)
    100 xp
    Inner join (3)
    100 xp
    50 xp
    Review inner join using on
    50 xp
    Inner join with using
    100 xp
    Self-ish joins, just in CASE
    50 xp
    100 xp
    Case when and then
    100 xp
    Inner challenge
    100 xp
  2. 2

    Outer joins and cross joins

    In this chapter, you'll come to grips with different kinds of outer joins. You'll learn how to gain further insights into your data through left joins, right joins, and full joins. In addition to outer joins, you'll also work with cross joins.

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  3. 3

    Set theory clauses

    In this chapter, you'll learn more about set theory using Venn diagrams and get an introduction to union, union all, intersect, and except clauses. You'll finish by investigating semi joins and anti joins, which provide a nice introduction to subqueries.

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In the following tracks

Data Analyst Data Analyst SQL FundamentalsSQL Server Fundamentals


filipschFilip SchouwenaarscolinricardoColin Ricardo


Introduction to SQL
Dr. Chester Ismay Headshot

Dr. Chester Ismay

Educator, Data Scientist, and R/Python Consultant

Chester enjoys helping others get into data science, figuring out how to best practice and improve on their skills, and working as a part-time consultant on R and Python programming projects. He is co-author of "Statistical Inference via Data Science: A ModernDive into R and the Tidyverse" available at and for purchase from CRC Press. He likes leading education and data science teams with the goal of improving best practices based on data from the learning sciences.
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