Difference Between `:decimal` and `:integer` in Rails Schema

# Difference Between `:decimal` and `:integer` in Rails Schema

In a Rails database schema, `:decimal` and `:integer` are two different data types that serve different purposes:

## `:integer`

- Stores whole numbers without fractional parts (e.g., 1, 42, -99)
- Takes up less storage space than decimal
- Suitable for counting values (beds, baths, parking spaces, etc.)
- Cannot represent fractional values
- In your schema, examples include: `beds`, `baths`, `sqft`, `built_year`, `lot_size`, `parking_spaces`

## `:decimal`

- Stores exact numeric values including fractional parts
- Takes precision and scale options:
  - `precision`: total number of digits
  - `scale`: number of digits after the decimal point
- Example: `decimal :latitude, precision: 10, scale: 6` can store numbers like 37.123456
- Ideal for financial calculations where precision is critical
- Prevents floating-point rounding errors
- In your schema, examples include: `pricing`, `property_tax`, `hoa`, `price_per_sqft`, `latitude`, `longitude`

## When to use which:

- Use `:integer` for:
  - Counts (number of bedrooms, bathrooms)
  - Years (built_year)
  - IDs and other whole numbers

- Use `:decimal` for:
  - Money/currency values (pricing, hoa fees)
  - Precise measurements requiring fractional parts
  - Geographic coordinates (latitude/longitude)
  - Percentages and rates

In your specific schema, you've correctly used `:integer` for whole number values like `beds`, `baths`, and `built_year`, while using `:decimal` for monetary values like `pricing`, `property_tax`, and `price_per_sqft`.

# Decimal Column Configuration for Numbers up to 99.99

Yes, `precision: 4, scale: 2` is exactly correct for storing numbers up to 99.99.

## How Decimal Precision and Scale Work

When defining a decimal column in Rails:

- **precision**: Total number of digits (both before and after the decimal point)
- **scale**: Number of digits after the decimal point

## For Your Example (99.99)

Breaking down your number:
- 2 digits before the decimal point (99)
- 2 digits after the decimal point (.99)
- Total: 4 digits

Therefore, `precision: 4, scale: 2` is the perfect configuration for numbers up to 99.99.

## In Migration Code

```ruby
add_column :table_name, :column_name, :decimal, precision: 4, scale: 2
```

Or when creating a table:

```ruby
create_table :table_name do |t|
  t.decimal :column_name, precision: 4, scale: 2
end
```

## Important Notes

1. This configuration will allow numbers from -99.99 to 99.99
2. If you try to store a larger number (like 100.00), it will cause an error
3. If you try to store a number with more decimal places (like 12.345), it will be rounded to 12.35

If you need to store larger numbers or more decimal places in the future, you would need to increase the precision and/or scale accordingly.

#ruby (17) #decimal (1) #rails (41) #type (1)

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