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  3. Introduction to SQL Server
  • 1

    SELECTion Box

    Free

    Hit the ground running by learning the basics of SELECT statements to retrieve data from one or more columns. You'll also learn how to apply filters to both numeric and text data, and sort the results.

  • 2

    Groups, strings, and counting things

    Herein, you'll learn how to use important SQL Server aggregate functions such as SUM, COUNT, MIN, MAX, and AVG. Following that, you'll learn how to manipulate text fields. To round out the chapter, you'll power up your queries using GROUP BY and HAVING, which will enable you to perform more meaningful aggregations.

  • 3

    Joining tables

    This chapter covers the basics of joining tables, using INNER, LEFT, and RIGHT joins, so that you can confidently retrieve data from multiple sources.

  • 4

    You've got the power

    In this final chapter, you'll get really hands on! You've worked with existing tables, but in this chapter, you'll get to CREATE and INSERT data into them. You'll also UPDATE existing records and practice DELETE statements in a safe environment. This chapter ensures the course gives you a thorough introduction to the key aspects of working with data in SQL Server.

Initializing

Exercise

Working with NULL values

A NULL value could mean 'zero' - if something doesn't happen, it can't be logged in a table. However, NULL can also mean 'unknown' or 'missing'. So consider if it is appropriate to replace them in your results. NULL values provide feedback on data quality. If you have NULL values, and you didn't expect to have any, then you have an issue with either how data is captured or how it's entered in the database.

In this exercise, you'll practice filtering for NULL values, excluding them from results, and replacing them with alternative values.

Instructions 1/2

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  • 1

    Use a shortcut to select all columns from grid. Then filter the results to only include rows where demand_loss_mw is unknown or missing.

  • 2

    Now filter the results to only include rows where demand_loss_mw is not unknown or missing.