Скачать или смотреть Get Total Sales for the Last 12 Months Using SQL

Discover how to get total sales from the last twelve months in SQL, even if there are null values. Learn the right query structure and techniques for accurate reporting.
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Solution to Getting Total Sales for the Last 12 Months in SQL

If you're working with SQL and need to analyze your sales data over the past year, you may encounter a common challenge: retrieving total sales values—even when some of the data entries are NULL. This can be particularly important for keeping track of performance and making informed business decisions.

In this guide, we will explore a comprehensive solution for obtaining total sales figures for the last 12 months, extending from the last month of the previous year to the current month of this year, regardless of any null values in your dataset.

Understanding the Problem

Using straightforward SQL queries might lead to incomplete data, where certain months display total sales as NULL. As a result, if you aim to view your total sales for each of the past twelve months—whether or not any sales occurred—you will need a query that can intelligently handle those gaps.

The Challenge

The initial query may only return data for months that have sales. For example, if your results look like this:

[[See Video to Reveal this Text or Code Snippet]]

You can see that you're missing data for the current year while only retrieving incomplete information for the previous year.

The Solution

Step 1: Setting Up the Query

To tackle this issue, you can modify your SQL code to create a recursive common table expression (CTE) that will generate all of the months necessary for the reporting period. The idea is to first establish relevant months and then gather data for those months, ensuring that even when no sales data exists, the month will still appear in the result set.

Here’s the SQL code you can use:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Breaking Down the Query

Setup Current and Prior Dates:

We define the current date (GETDATE()) and calculate the date one year prior using DATEADD().

Define Relevant Months:

We create a CTE (relevant_months) that recursively generates a list of months for the last year.

Gather Relevant Sales Data:

Another CTE (relevant_data) collects all sales records from the past year, ensuring that only relevant entries are considered.

Combine Data:

The final SELECT statement combines the months from relevant_months with the sales data from relevant_data, utilizing a LEFT JOIN to include all months, even those without sales data.

Group and Order the Results:

The results are grouped by month and year, ensuring that the total sales are calculated properly, and then ordered chronologically.

Conclusion

By utilizing this structured approach, you can confidently retrieve total sales for every month over the past year, while ensuring that any months without sales appear with a total of NULL. This not only enhances the visibility of your sales data but also provides crucial insights for business analysis.

Feel free to adjust the query as needed for your specific dataset, and happy querying!