Introduction to JOIN

This introductory guide to SQL is soon coming to an end, and you’ll be able to go out and perform analysis for your business using SQL. But before that, there’s one last important thing to add to your toolbox: combining different tables into one. This is done with the join function.

Remember the different ways to control the height and width of tables? The join function increases the width of the resulting table by adding columns from other tables. The join function in SQL can work in a quite advanced way, with many different variations (left, right, inner, outer, etc.). But the ‘left join’ function is by far the most frequently used, so this is the focus in this guide.