SQL Tutorial: All about joins

Want to learn more? Take the full course at https://learn.datacamp.com/courses/improving-query-performance-in-postgresql at your own pace. More than a video, you'll learn hands-on coding & quickly apply skills to your daily work. --- Welcome. My name is Amy McCarty, I am a data analyst, and I work in SQL to gather data for analysis to drive business insight. Sometimes this data comes from multiple sources, and sometimes there's a lot. In this course, you will learn to elegantly and efficiently combine data. We will cover choices in query structure, including join types, subqueries, and temporary tables. We will discuss limiting and aggregating data from large tables. We will cover database storage properties and how these characteristics impact the available optimization tools. Finally, we will view each concept through the lens of the query planner. Imagine you are at a restaurant. Your order is the query or SQL instructions. You SELECT your food FROM the menu. The waiter takes the request to the kitchen. The cooks determine how to best execute it. The cooks create the actual steps that return food. They transform your order into a meal that arrives quickly with the entree ready before the dessert but after the appetizer. The cooks create the optimal execution plan to translate your query into a meal. Sometimes you order an entree then drink, and have the drink arrive first. Similarly, queries also are not processed in the given, written order. SELECT statements provide a list of ingredients. FROM statements provide the directions to these ingredients. We will explore how different ordering and structures impact the query plan and execution. We will start with joins. Joins are one way to combine data from different tables. A table on sales orders may contain a customer number, but the detailed customer information is stored in a separate customer information LOOKUP table. Joins are a way to combine these tables, combining data to build a more comprehe