Improving Query Performance in SQL Server

Overview

In this course, students will learn to write queries that are both efficient and easy to read and understand.

A mission critical assignment is depending on your SQL coding skills. You’ve been given some code to fix. It is giving the results you need but it’s running too slow, and it’s poorly formatted making it hard to read. The deadline is tomorrow. You’ll need to reformat the code and try different methods to improve performance. The pressure is on!!! In this course we’ll be using SQL on real world datasets, from sports and geoscience, to look at good coding practices and different ways how we can can improve the performance of queries to achieve the same outcome.

Syllabus

Introduction, Review and The Order of Things

In this chapter, students will learn how SQL code formatting, commenting, and aliasing is used to make queries easy to read and understand. Students will also be introduced to query processing order in the database versus the order of the SQL syntax in a query.

Filtering and Data Interrogation

This chapter introduces filtering with WHERE and HAVING and some best practices for how (and how not) to use these keywords. Next, it explains the methods used to interrogate data and the effects these may have on performance. Finally, the chapter goes over the roles of DISTINCT() and UNION in removing duplicates and their potential effects on performance.

Sub-queries and presence or absence

This chapter is an introduction to sub-queries and their potential impacts on query performance. It also examines the different methods used to determine if the data in one table is present, or absent, in a related table.

Query performance tuning

Students are introduced to how STATISTICS TIME, STATISTICS IO, indexes, and executions plans can be used in SQL Server to help analyze and tune query performance.