Introduction to Data Joins

In the world of data, a “join” is like merging information from different sources into a unified result. To do this, it needs a condition – typically a shared column – to link the sources together. Think of it as finding common ground between different datasets.

In SQL, these sources are referred to as “tables,” and the result of using a JOIN clause is a new table. Fundamentally, traditional (batch) SQL joins operate on static datasets, where you have prior knowledge of the number of rows and the content within the source tables before executing the Join. These join operations are typically simple to implement and computationally efficient. However, the dynamic and unbounded nature of streaming data presents unique challenges for performing joins in near-real-time scenarios.