Book Image

The Applied SQL Data Analytics Workshop - Second Edition

By : Matt Goldwasser, Upom Malik, Benjamin Johnston
3.5 (2)
Book Image

The Applied SQL Data Analytics Workshop - Second Edition

3.5 (2)
By: Matt Goldwasser, Upom Malik, Benjamin Johnston

Overview of this book

Every day, businesses operate around the clock and a huge amount of data is generated at a rapid pace. Hidden in this data are key patterns and behaviors that can help you and your business understand your customers at a deep, fundamental level. Are you ready to enter the exciting world of data analytics and unlock these useful insights? Written by a team of expert data scientists who have used their data analytics skills to transform businesses of all shapes and sizes, The Applied SQL Data Analytics Workshop is a great way to get started with data analysis, showing you how to effectively sieve and process information from raw data, even without any prior experience. The book begins by showing you how to form hypotheses and generate descriptive statistics that can provide key insights into your existing data. As you progress, you'll learn how to write SQL queries to aggregate, calculate and combine SQL data from sources outside of your current dataset. You'll also discover how to work with different data types, like JSON. By exploring advanced techniques, such as geospatial analysis and text analysis, you'll finally be able to understand your business at a deeper level. Finally, the book lets you in on the secret to getting information faster and more effectively by using advanced techniques like profiling and automation. By the end of The Applied SQL Data Analytics Workshop, you'll have the skills you need to start identifying patterns and unlocking insights in your own data. You will be capable of looking and assessing data with the critical eye of a skilled data analyst.
Table of Contents (9 chapters)
Preface
7
7. The Scientific Method and Applied Problem Solving

6. Performant SQL

Activity 6.01: Query Planning

Note that the performance metrics produced by the output of query execution plan will vary based on system configuration.

Solution

  1. Open PostgreSQL and connect to the sqlda database:
    C:\> psql sqlda
  2. Use the EXPLAIN command to return the query plan for selecting all available records within the customers table:
    sqlda=# EXPLAIN SELECT * FROM customers;

    This query will produce the following output from the planner:

    Figure 6.63: Plan for all records within the customers table

    The setup cost is 0, the total query cost is 1536, the number of rows is 50000, and the width of each row is 140. The cost is actually in cost units, the number of rows is in rows, and the width is in bytes.

  3. Repeat the query from step 2 of this activity, this time limiting the number of returned records to 15:
    sqlda=# EXPLAIN SELECT * FROM customers LIMIT 15;

    This query will produce the following output from the planner:

    Figure 6.64: Plan for all records...