Joins

Abstract

I’ve been a database guy for going on 20 years now. For at least the last 15 years I’ve been explaining joins. It’s a tricky topic. When writing queries in SQL, joins can get out of hand quickly. One of the things that impresses me the most about the Tableau products are how effective they are in giving the end user the ability to do complex things while hiding the complexity from that user. The visual join designer is the best example of this genius. In this chapter we will dive deep into LEFT, RIGHT, INNER, and OUTER joins. We will look at joins that return records that match and joins that return only unmatched records, and we’ll do all of this without ever writing a single line of SQL. If you already know how to write a query, I think you will be pleasantly surprised at the visual tools Prep gives us; if you don’t know a thing about queries and have no interest in them, I think you will be thrilled at the power and flexibility this tool puts in your hands.