Resolving the NEW_KPI Identifier Issue: Subtracting Columns with Case Conditions in Oracle SQL

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Discover how to correctly subtract two columns using case conditions in Oracle SQL for a smooth implementation in Apex Interactive Grid.
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Resolving the NEW_KPI Identifier Issue: Subtracting Columns with Case Conditions in Oracle SQL

When working with Oracle SQL, particularly in the context of Apex and Interactive Grids, you may encounter various challenges. One common issue involves the subtraction of columns—specifically when those columns have case conditions.

In this guide, we will address a specific scenario: subtracting values from two columns derived from case statements in an Oracle SQL query. Let’s dive into the problem and discover a clear solution.

The Problem: Subtracting Columns with Case Conditions

You are working with a source query in an Oracle Apex Interactive Grid, and you have two float columns in your database:

KPI_1: A straightforward column.

KPI_2 and KPI_3: Derived via a case statement based on the department value.

Your goal is to generate a third virtual column that represents the result of subtracting NEW_KPI from CURRENT_KPI. However, running a query like this often results in an "invalid identifier" error for NEW_KPI:

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

Understanding the Error

The error arises because SQL does not recognize NEW_KPI as a valid identifier when trying to use it in the same select statement. SQL processes the select statement left to right, so NEW_KPI hasn't been defined yet when you're trying to use it in the RESULT calculation.

The Solution: Rewriting Your Query

To resolve the issue, you can repeat the logic used to derive NEW_KPI in the calculation of your RESULT. Here's how to do that:

Step 1: Rewrite the Query

Instead of attempting to reference NEW_KPI, you should embed the case statement directly in the calculation of RESULT. The updated query will look like this:

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

Step 2: Alternative Concatenation for Efficiency

If you want a condensed version that concatenates the outputs into a single string, you can adjust your query as follows:

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

Why This Works

Explicit Calculation: By including the case statement directly within the subtraction, SQL can effectively compute RESULT.

Formatting: The to_char function formats the numbers as you need for display purposes, while maintaining the numeric integrity for calculations.

Conclusion

Working around identifier issues in SQL can be tricky, but understanding how to structure your queries will save you time and frustration. By embedding your case logic within your calculations, you can avoid "invalid identifier" errors and successfully manipulate your data as needed.

We hope this post helps you in your Oracle SQL journey, particularly when dealing with complex queries within Apex. If you have any questions or further challenges, feel free to leave comments below!