A SQL join is a Structured Query Language (SQL) instruction to combine data from two sets of data (e.g. two tables). Before we dive into the details of a SQL join, let’s briefly discuss what SQL is, and why someone would want to perform a SQL join.
SQL is a special-purpose programming language designed for managing information in a relational database management system (RDBMS). The word relational here is key; it specifies that the database management system is organized in such a way that there are clear relations defined between different sets of data.
Typically, you need to extract, transform, and load data into your RDBMS before you’re able to manage it using SQL, which you can accomplish by using a tool like Stitch.