Book Image

SQL Query Design Patterns and Best Practices

By : Steve Hughes, Dennis Neer, Dr. Ram Babu Singh, Shabbir H. Mala, Leslie Andrews, Chi Zhang
5 (1)
Book Image

SQL Query Design Patterns and Best Practices

5 (1)
By: Steve Hughes, Dennis Neer, Dr. Ram Babu Singh, Shabbir H. Mala, Leslie Andrews, Chi Zhang

Overview of this book

SQL has been the de facto standard when interacting with databases for decades and shows no signs of going away. Through the years, report developers or data wranglers have had to learn SQL on the fly to meet the business needs, so if you are someone who needs to write queries, SQL Query Design and Pattern Best Practices is for you. This book will guide you through making efficient SQL queries by reducing set sizes for effective results. You’ll learn how to format your results to make them easier to consume at their destination. From there, the book will take you through solving complex business problems using more advanced techniques, such as common table expressions and window functions, and advance to uncovering issues resulting from security in the underlying dataset. Armed with this knowledge, you’ll have a foundation for building queries and be ready to shift focus to using tools, such as query plans and indexes, to optimize those queries. The book will go over the modern data estate, which includes data lakes and JSON data, and wrap up with a brief on how to use Jupyter notebooks in your SQL journey. By the end of this SQL book, you’ll be able to make efficient SQL queries that will improve your report writing and the overall SQL experience.
Table of Contents (21 chapters)
1
Part 1: Refining Your Queries to Get the Results You Need
6
Part 2: Solving Complex Business and Data Problems in Your Queries
11
Part 3: Optimizing Your Queries to Improve Performance
14
Part 4: Working with Your Data on the Modern Data Platform

The impact of indexes on query design

As we know, indexes improve the read performance of queries, so we should always keep in mind the columns that participate in the JOIN, WHERE, GROUP BY, HAVING, and ORDER BY clauses must have an index. This is because columns participating in the JOIN and WHERE clauses are the deciding factor and are read/accessed first from the raw data. Then all other filters are applied, such as GROUP BY, HAVING, and ORDER BY, based on the result set and the functions used in the queries.

If you write a query that has an index on the column being used in the WHERE clause for filtering the data, its performance will be drastically better after we run the same query after creating the index on that column. This applies to the columns participating in the JOIN, GROUP BY, HAVING, and ORDER BY clauses.

To further improve performance, you should include the columns participating in the SELECT statement, and if you are going to create a report for a particular...