How to Display Vertical Results to Horizontal in SQL

Learn how to effectively convert vertical results into horizontal format using SQL and T-SQL techniques. Discover practical examples with easy-to-follow explanations.
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How to Display Vertical Results to Horizontal in SQL

In the world of database management, it’s often necessary to transform vertical data into a horizontal layout. This can be particularly useful when you want to create reports or when you need to analyze data in a more user-friendly format. In this post, we’ll explore how to achieve this transformation specifically using SQL Server and T-SQL.

Understanding the Problem

Consider a scenario where you have a SQL query that returns data in a vertical format—this means that for every unique item, there are multiple rows of corresponding values.

Example: Current Query Result

Here’s an example of such a vertical output:

ITEMDESCRIPTIONALTERNATE489TJ CLASSIC PE 1KG635489TJ CLASSIC PE 1KG859490CAKE FLOUR 250G251490CAKE FLOUR 250G278490CAKE FLOUR 250G703490CAKE FLOUR 250G925The challenge is to convert this vertical format into a horizontal one, where all related values appear in the same row for each unique item. The expected horizontal output looks like this:

ITEMDESCRIPTIONALTERNATEALTERNATE1ALTERNATE2ALTERNATE3489TJ CLASSIC PE 1KG635859490CAKE FLOUR 250G251278703925The Solution

To tackle this problem in SQL Server, we can utilize the combination of the ROW_NUMBER window function and pivoting logic. Let's break it down step-by-step.

Step 1: Create a Common Table Expression (CTE)

We'll start by using a Common Table Expression (CTE) to assign a unique row number to each ALTERNATE value within each ITEM group.

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ROW_NUMBER(): This function provides a unique sequential number to rows within a partition of a dataset.

PARTITION BY: It divides the result set into partitions to which the ROW_NUMBER() function is applied.

Step 2: Aggregate the Data

Next, we will select from the CTE and aggregate the data. For each ITEM, we will fetch the maximum ALTERNATE values based on the assigned row numbers.

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

MAX(CASE WHEN ...): This method is used to conditionally select values from each row based on its assigned row number.

GROUP BY: Groups the results by ITEM and DESCRIPTION to create a single row for each item with multiple alternate values displayed horizontally.

Full Query Example

Combining both steps, here’s the complete SQL query to convert vertical results to horizontal:

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

Conclusion

Transforming vertical query results into a horizontal format is straightforward with the use of SQL’s ROW_NUMBER function and an appropriate aggregate query. By mastering this technique, you can significantly improve the readability and presentation of your data, making it easier to analyze and report.

Now you can display your results the way you want! Happy querying!