In this chapter, you’ll be introduced to the concept of joining tables and will explore all the ways you can enrich your queries using joins—beginning with inner joins.

The ins and outs of INNER JOIN

Your first join

Joining with aliased tables

USING in action

Defining relationships

Relationships in our database

Inspecting a relationship

Multiple joins

Joining multiple tables

Checking multi-table joins

Introducing Inner Joins

After familiarizing yourself with inner joins, you will come to grips with different kinds of outer joins. Next, you will learn about cross joins. Finally, you will learn about situations in which you might join a table with itself.


LEFT and RIGHT JOINs

Remembering what is LEFT

This is a LEFT JOIN, right?

Building on your LEFT JOIN

Is this RIGHT?

FULL JOINs

Comparing joins

Chaining FULL JOINs

Crossing into CROSS JOIN

Histories and languages

Choosing your join

Self joins

Comparing a country to itself

All joins on deck

Outer Joins, Cross Joins and Self Joins

In this chapter, you will learn about using set theory operations in SQL, with an introduction to UNION, UNION ALL, INTERSECT, and EXCEPT clauses. You’ll explore the predominant ways in which set theory operations differ from join operations.


Set theory for SQL Joins

UNION vs. UNION ALL

Comparing global economies

Comparing two set operations

At the INTERSECT

INTERSECT

Review UNION and INTERSECT

EXCEPT

You've got it, EXCEPT...

Calling all set operators

Set Theory for SQL Joins

In this closing chapter, you’ll begin by investigating semi-joins and anti-joins. Next, you'll learn how to use nested queries. Last but not least, you’ll wrap up the course with some challenges!


Subquerying with semi joins and anti joins

Multiple WHERE clauses

Semi join

Diagnosing problems using anti join

Subqueries inside WHERE and SELECT

Subquery inside WHERE

WHERE do people live?

Subquery inside SELECT

Subqueries inside FROM

Subquery inside FROM

Subquery challenge

Final challenge

The finish line

Subqueries

Countries

Leaders

Diagrams

Joining data is an essential skill that enables us to draw information from separate tables together into a single, meaningful set of results. Learn to supercharge your queries using table joins and relational set theory in this course on joining data. In this course, you’ll learn how to work with more than one table in SQL, use inner joins, outer joins, and cross joins, leverage set theory, including unions, intersect, and except clauses, and create nested queries. Every step is accompanied by exercises and opportunities to apply the theory and grow your confidence in SQL.

Joining data is an essential skill in data analysis, enabling you to draw information from separate tables together into a single, meaningful set of results. In this comprehensive course on joining data, you'll delve into the intricacies of table joins and relational set theory, learning how to optimize your queries for efficient data retrieval.
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<h2>Understand Data Joining Fundamentals</h2>

You will learn how to work with multiple tables in SQL by navigating and extracting data from various tables within a SQL database using various join types, including inner joins, outer joins, and cross joins. With practice, you'll gain the knowledge of how to select the appropriate join method.
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<h2>Explore Advanced Data Manipulation Techniques</h2>

Next up, you'll explore set theory principles such as unions, intersects, and except clauses, as well as discover the power of nested queries in SQL. 

Every step is accompanied by exercises and opportunities to apply the theory and grow your confidence in SQL.

Intermediate SQL

Supercharge your SQL queries by learning to join tables together, apply relational set theory to table joins, and work with subqueries.

Joining Data in SQL

Level up your SQL knowledge and learn to join tables together, apply relational set theory, and work with subqueries. 

USING in action

Joining Data in SQL

Exercise instructions

Hands-on interactive exercise