SQL Interest Calculator

A collection of SQL Server functions, a stored procedure, and a table-valued function for general interest calculation.
Developed during my internship at ASEE by Asseco as part of a banking system environment.

📌 Overview

This project provides reusable SQL utilities to calculate financial interest between two dates with flexible parameters.
It is designed for banking and financial use cases, but the logic is generic enough to apply in other domains.

🚀 Features

• Multiple interest calculation methods:
  • Proporc. (Proportional)
  • 30/360
  • 28–31/365
  • 30/365-6
  • Compound
  • Anticipative options
• Validates input dates and parameters
• Returns precise decimal values with rounding
• Two ways to use:
  • Stored procedure (sp_CalcInterest) → returns results in a queryable resultset
  • Table-valued function (fn_CalcInterest) → can be embedded directly in SELECT queries

⚙️ Installation (simple)

1. Open your target database in SSMS (or any SQL client).
2. Run the scripts:
   • sql/procedures/sp_CalcInterest.sql (procedure)
   • sql/functions/fn_CalcInterest.sql (table-valued function)
3. That’s it — both are now available in the current database.

▶️ Run Examples

• Stored Procedure

EXEC dbo.sp_CalcInterest
  @Method = 'ACT/ACT',
  @StartDate = '2023-01-01',
  @EndDate   = '2023-12-31',
  @Principal = 10000,
  @RatePct   = 5,
  @IsAnticipative = 0;

• Table-Valued Function

SELECT *
FROM dbo.fn_CalcInterest(
  'ACT/ACT',
  '2023-01-01',
  '2023-12-31',
  10000,
  5,
  0
);

📤 Output Columns

• Normal:

Start Date	End Date	Days	Rate %	Method	Principal (initial)	Interest (normal)	New Balance
2023-01-01	2023-12-31	364	5.00	ACT/365	10000.00	498.63	10498.63

• Anticipative:

Start Date	End Date	Days	Rate %	Method	Principal (final)	Principal (anticip)	Interest (anticip)
2023-07-01	2023-08-15	44	11.00	30/360	250000.00	239103.45	10896.55

📚 Notes

• This repository was created as part of my internship at ASEE by Asseco.
• It is intended for educational/demo purposes and may not reflect production-grade financial software.

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👤 Author: Gegë Dobruna (Intern at ASEE by Asseco)
📅 Year: 2025