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Learn how to return a custom record in PostgreSQL with calculated employee ranks using PL/pgSQL functions. Make complex queries easy with this step-by-step guide!
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This video is based on the question https://stackoverflow.com/q/64628385/ asked by the user 'Zoey Malkov' ( https://stackoverflow.com/u/9547778/ ) and on the answer https://stackoverflow.com/a/64628561/ provided by the user 'Marc' ( https://stackoverflow.com/u/1024832/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Return a Custom Record with Calculated Data in PostgreSQL

Managing employee data in a database can often involve complex calculations to derive new insights. One common requirement might be to return a custom record with calculated fields based on existing data. In this post, we will explore how to return a custom employee record with new ranks calculated from the existing ranks in a PostgreSQL database.

Understanding the Problem

You've created a database table named ‘employees’ which includes the columns for employee IDs, names, and ranks. The challenge is to return new records containing the employee names and their newly calculated ranks without changing the existing SELECT statement criteria.

You want the final output to look like this:

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Setting Up the Employee Table

Before diving into the solution, let's set the stage by reviewing the existing database setup.

1. Creating the Employee Table

First, you need to create an employee table to store relevant data:

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Next, you'll insert some sample data:

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2. Defining a Custom Record Type

You must also define a custom record type to hold the data structure for the output:

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Crafting the Calculation Function

Now that we have the basic setup ready, let’s focus on creating a function that will calculate the new ranks based on the existing employee ranks.

1. Creating the Calculation Function

Your function will iterate through the employees and return a custom record for each employee with calculated ranks. Here's an example of how you can structure this function using PL/pgSQL:

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2. Invoking Your Function

Once your function is defined, you can call it in a SELECT statement to fetch the calculated records:

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This will return the custom records with the names of employees and their newly calculated ranks.

Summarizing Results with Total

If you want to include a total at the end of your result set, you can use a UNION statement to append a summary row to your output:

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Final Output Example

Using the logic mentioned above, you can anticipate results like this:

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Conclusion

Returning a custom record with calculated data in PostgreSQL can easily be achieved with a solid understanding of database functions and PL/pgSQL. By creating a function that processes existing data and returns newly calculated results, you can efficiently summarize and manage your employee data. With this knowledge, you can enhance your SQL queries and deliver more robust insights from your database.

Whether you're managing a small team or a large organization, the ability to perform these calculations will streamline your data handling and reporting efforts. Now you are equipped to implement this in your database applications!