From the course: Fundamentals of Data Transformation for Data Engineering

Unlock the full course today

Join today to access over 24,100 courses taught by industry experts.

Joins and comparisons

Joins and comparisons - SQL Tutorial

From the course: Fundamentals of Data Transformation for Data Engineering

Start my 1-month free trial Buy for my team

Joins and comparisons

“

- [Instructor] In this lesson, we're going to jump into joins and comparisons, and those are ways of filtering your data and comparing them for future data transformation steps. So we'll start by loading our data set, and in our previous examples, we used where to filter queries, but we can also do that with joins. But there's a caveat, and that is that we need to be very careful with how joins work. So if I run this query, we're selecting parks, we're joining in our visitor centers table. And you can imagine there might be many visitor centers in one park. That is, there's a one-to-many relationship between parks and visitor centers, and we're joining those in on parkcode. But more importantly, we're filtering where the designation equals national monument, and the visitor center is a passport stamp location. Now, there's an important piece here. Also, I'll call out that I use this one equals one syntax quite often. Obviously, one does in fact equal one. That's just to be sure that…

Contents