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SQL Query Design Patterns and Best Practices

SQL Query Design Patterns and Best Practices

By : Steve Hughes, Steven Hughes, Dennis Neer, Dr. Ram Babu Singh, Shabbir H. Mala, Leslie Andrews, Chi Zhang, Neer, Ram Babu Singh, Shabbir Mala, Andrews, Zhang
4.7 (11)
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SQL Query Design Patterns and Best Practices

SQL Query Design Patterns and Best Practices

4.7 (11)
By: Steve Hughes, Steven Hughes, Dennis Neer, Dr. Ram Babu Singh, Shabbir H. Mala, Leslie Andrews, Chi Zhang, Neer, Ram Babu Singh, Shabbir Mala, Andrews, 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)
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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

Creating a recursive CTE

A recursive CTE is one where the query references itself. Think of a list of employees and the person who manages them, a parent/child relationship, a bill of materials, or other organizational/hierarchical situations. These are the types of relationships you can express using a recursive CTE.

In this section, we will examine how to take that relationship and show all the levels of a hierarchy using a CTE. We will first need to create some data to use, and then we will create a query that shows all the levels of an organizational hierarchy.

Creating the hierarchical data

The WorldWideImporters database doesn’t have any tables with a parent/child relationship, so we are going to create a simple Employee table and populate it with some data to use:

-- Create an Employee table.
CREATE TABLE dbo.Employee
(
EmpID SMALLINT NOT NULL,
FirstNm NVARCHAR(30) NOT NULL,
LastNm NVARCHAR(40) NOT NULL,
JobTitle NVARCHAR(50) NOT NULL,
ManagerID SMALLINT NULL...

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