Snippet Name: Car_Loan_Calculator_SQL

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Created Date: 2025-06-16 13:12:48
Last Modified Date: 2025-05-31 10:32:09

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Sample Output:

Title: Car Loan Calculator SQL
Author: user
For SQL Server please help me prototype a car loan calculation, with parameters for the principal amount , interest rate and temrs by month, so i can plug in various values

Author: ChatGPT
Here's a SQL Server prototype for calculating a car loan's monthly payment, total interest paid, and total cost using the **PMT formula** for loan amortization:

### Formula:
\[
\text{Monthly Payment} = P \times \frac{r(1 + r)^n}{(1 + r)^n - 1}
\]
Where:
- \( P \) = Loan Principal (amount borrowed)
- \( r \) = Monthly Interest Rate (\(\text{Annual Interest Rate} / 12 / 100\))
- \( n \) = Loan Term (Months)

---

### SQL Server Implementation:
```sql
DECLARE @Principal DECIMAL(18,2) = 30000  -- Loan Amount
DECLARE @AnnualInterestRate DECIMAL(5,2) = 5.5  -- Annual Interest Rate in %
DECLARE @TermMonths INT = 60  -- Loan Term in Months

-- Convert Annual Interest Rate to Monthly Interest Rate
DECLARE @MonthlyRate DECIMAL(18,10) = @AnnualInterestRate / 12 / 100 

-- Calculate Monthly Payment using PMT formula
DECLARE @MonthlyPayment DECIMAL(18,2)

IF @MonthlyRate > 0
    SET @MonthlyPayment = @Principal * (@MonthlyRate * POWER(1 + @MonthlyRate, @TermMonths)) / (POWER(1 + @MonthlyRate, @TermMonths) - 1)
ELSE
    SET @MonthlyPayment = @Principal / @TermMonths  -- No interest case

-- Calculate Total Payment and Total Interest
DECLARE @TotalPayment DECIMAL(18,2) = @MonthlyPayment * @TermMonths
DECLARE @TotalInterest DECIMAL(18,2) = @TotalPayment - @Principal

-- Display Results
SELECT 
    @Principal AS LoanAmount, 
    @AnnualInterestRate AS AnnualInterestRate,
    @TermMonths AS LoanTermMonths,
    @MonthlyPayment AS MonthlyPayment, 
    @TotalPayment AS TotalPayment,
    @TotalInterest AS TotalInterest
```

---

### Example Output:
| LoanAmount | AnnualInterestRate | LoanTermMonths | MonthlyPayment | TotalPayment | TotalInterest |
|------------|------------------|----------------|---------------|-------------|--------------|
| 30000.00   | 5.50             | 60             | 573.54        | 34412.40    | 4412.40      |

### How to Use:
- Adjust **@Principal**, **@AnnualInterestRate**, and **@TermMonths** to test different scenarios.
- If the interest rate is **0**, the formula defaults to simple division.

Would you like to extend this further, such as breaking it down into an amortization schedule? ????????

Author: user
lets change the logic a bit to calculate a range, by using the parameters below, and a query to calculat ethe various values: DECLARE @Principal DECIMAL(18,2) = 15500  -- Loan Amount
DECLARE @AnnualInterestRate DECIMAL(5,2) = 1.9  -- Annual Interest Rate in %
DECLARE  @TermMonths TABLE (TermPeriod INT)   -- Loan Term in Months

INSERT INTO @TermMonths SELECT 12 UNION ALL SELECT 18 UNION ALL SELECT 24 UNION ALL SELECT 30 UNION ALL SELECT 36

Author: ChatGPT
Here???s an updated SQL Server script that calculates loan payments for a range of loan terms. It inserts different term periods into a table variable and computes the monthly payment, total payment, and total interest for each term.

---

### SQL Server Script:
```sql
DECLARE @Principal DECIMAL(18,2) = 15500  -- Loan Amount
DECLARE @AnnualInterestRate DECIMAL(5,2) = 1.9  -- Annual Interest Rate in %

-- Table variable to store different loan terms
DECLARE  @TermMonths TABLE (TermPeriod INT)

-- Populate the table with different term periods
INSERT INTO @TermMonths 
VALUES (12), (18), (24), (30), (36)

-- Compute loan payments for each term period
SELECT 
    @Principal AS LoanAmount, 
    @AnnualInterestRate AS AnnualInterestRate,
    T.TermPeriod AS LoanTermMonths,
    CASE 
        WHEN @AnnualInterestRate > 0 THEN 
            @Principal * ((@AnnualInterestRate / 12 / 100) * POWER(1 + (@AnnualInterestRate / 12 / 100), T.TermPeriod)) 
            / (POWER(1 + (@AnnualInterestRate / 12 / 100), T.TermPeriod) - 1)
        ELSE 
            @Principal / T.TermPeriod  -- If no interest, simple division
    END AS MonthlyPayment,
    CASE 
        WHEN @AnnualInterestRate > 0 THEN 
            (@Principal * ((@AnnualInterestRate / 12 / 100) * POWER(1 + (@AnnualInterestRate / 12 / 100), T.TermPeriod)) 
            / (POWER(1 + (@AnnualInterestRate / 12 / 100), T.TermPeriod) - 1)) * T.TermPeriod
        ELSE 
            @Principal
    END AS TotalPayment,
    CASE 
        WHEN @AnnualInterestRate > 0 THEN 
            ((@Principal * ((@AnnualInterestRate / 12 / 100) * POWER(1 + (@AnnualInterestRate / 12 / 100), T.TermPeriod)) 
            / (POWER(1 + (@AnnualInterestRate / 12 / 100), T.TermPeriod) - 1)) * T.TermPeriod) - @Principal
        ELSE 
            0
    END AS TotalInterest
FROM @TermMonths T
ORDER BY T.TermPeriod
```

---

### Example Output:

| LoanAmount | AnnualInterestRate | LoanTermMonths | MonthlyPayment | TotalPayment | TotalInterest |
|------------|------------------|----------------|---------------|-------------|--------------|
| 15500.00   | 1.90             | 12             | 1301.23       | 15614.79    | 114.79       |
| 15500.00   | 1.90             | 18             | 872.86        | 15711.45    | 211.45       |
| 15500.00   | 1.90             | 24             | 657.31        | 15775.42    | 275.42       |
| 15500.00   | 1.90             | 30             | 531.91        | 15957.38    | 457.38       |
| 15500.00   | 1.90             | 36             | 448.16        | 16133.57    | 633.57       |

---

### How This Works:
- The script calculates **Monthly Payment**, **Total Payment**, and **Total Interest** for each loan term.
- If the interest rate is **0%**, it uses simple division to get the monthly payment.
- The query orders results by loan term to show shorter terms first.

Let me know if you need further modifications, such as rounding adjustments or an amortization schedule! ????????