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

Understanding index maintenance

Over time, indexes get fragmented due to write (UPDATE, DELETE, and INSERT) operations on the table on which indexes exist, which causes read operations to slow down as the SQL server now must scan a greater number of pages in the index due to the fragmentation. Therefore, we must keep track of the indexes used and the fragmentation in the indexes and should address the fragmentation to keep indexes healthy.

Now, this brings us to the topic of identifying fragmentation in indexes and to address fragmentation in indexes to keep them healthy. So, let’s discuss index health and defragmenting the index next.

Index health

To identify fragmented indexes, we must check all the indexes where the average fragmentation is more than zero. To get the list of fragmented indexes, use the following standard query, which uses the catalog views to read the system data:

SELECT OBJECT_NAME(IND.OBJECT_ID) AS [Table Name],
IND.NAME AS [Index Name], PS...