Скачать или смотреть How to subtract from one row the other rows in SQL Clickhouse

Learn how to efficiently `subtract` values from different rows in SQL Clickhouse with a practical example and clear SQL code.
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Solving the Problem of Row Subtraction in SQL Clickhouse

Working with data in SQL can sometimes present unique challenges, especially when it comes to manipulating numeric values from various rows. One such challenge is the need to subtract the values of multiple rows from a single row. In this guide, we'll explore a specific example using Clickhouse, a powerful columnar database management system, and show you how to solve this problem effectively.

The Challenge

Imagine you have executed the following SQL query:

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

This query results in a summary table structured as below:

sourcesumall100source 11source 21source 31Now, you want to add an additional row to this table that represents the result of subtracting the sums of source 1, source 2, and source 3 from all. Specifically, you want the value 100 - 1 - 1 - 1 which equals 97, displayed as follows:

sourcesumall100source 11source 21source 31diff97Let’s dive into crafting a solution to achieve this.

The Solution

To conduct the subtraction of specific row sums gracefully while using Clickhouse, you can utilize the following SQL query:

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

Breaking Down the Query

Array Grouping: The query begins by grouping the sums of the sources using groupArrayIf. This allows us to isolate the values of source='all' and those not equal to 'all' into two separate arrays (denoted as sa and ss respectively).

Calculation of Differences: Subsequently, the difference is calculated by subtracting the total sum of source values (found in ss) from the total sum of all values (in sa). This results in a new tuple for the difference.

Flattening and Joining: Finally, the result is formatted using arrayJoin, which aids in displaying the computed values neatly, allowing for the addition of the new "diff" row to your table.

Result of the Query

Executing the above SQL code produces the following output:

sourcesumall100source 11source 21source 31diff97Conclusion

In conclusion, subtracting values from different rows in Clickhouse can be achieved using a combination of SQL functions for grouping, array manipulation, and mathematical operations. The method described in this post not only solves the problem at hand but also provides a clear template that can be adapted for similar situations you may encounter while handling data analytics in SQL.

If you faced similar challenges or have questions regarding SQL selections or Clickhouse, feel free to drop a comment below, and let's discuss!