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)
Part 1: Refining Your Queries to Get the Results You Need
Part 2: Solving Complex Business and Data Problems in Your Queries
Part 3: Optimizing Your Queries to Improve Performance
Part 4: Working with Your Data on the Modern Data Platform

Creating CTEs

Creating a CTE is not a complex process. It is a simple query that defines the name of the CTE and then uses it:

;  --previous line must have a ; terminator
ISODates as (
SELECT distinct [Date]
      ,[ISO Week Number] as [ISOWeekNumber]
  FROM [Dimension].[Date])
SELECT Date, [ISOWeekNumber]

The query gets the distinct list of Date instances and ISO Week Number from Date Dimension in the WorldWideImportersDW database sample. The start of the query is the with keyword, which has a semi-colon terminating the line before it. Next is the name you will use to refer to the CTE in any future queries, in this case, ISODates. The query renames ISO Week Number to ISOWeekNumber. The final step is to write a query that selects from or uses the CTE table that was created. Refer to the following figure:

Figure 5.1 – A complete CTE query and the result set from the WorldWideImportersDW...