Working with Floating-Point Numbers in Android's SQLite Database

SQLite uses a storage class called REAL to store floating-point numbers. This can handle both double and float values. When inserting data, you'll use methods of the ContentValues class to specify the column name and the floating-point value.

Here's an example:

// ... (get a writable database)

ContentValues values = new ContentValues();
values.put("columnName", yourDoubleValue); // Use put for double

// Alternatively, for float values with an 'f' suffix
values.put("columnName", yourFloatValue + "f"); 

db.insertOrThrow(TABLE_NAME, null, values);

Important Note:

• Don't convert the double or float value to a String directly. This might cause loss of precision.
• SQLite stores floating-point numbers using 8 bytes, which can accommodate both double and float with good precision.

Additional Considerations:

• For storing currency values or other data requiring high precision, consider using fixed-point arithmetic instead of double or float. This can improve accuracy, especially for financial calculations.

public class MyDatabaseHelper extends SQLiteOpenHelper {

    // Database information
    private static final String DATABASE_NAME = "myDatabase.db";
    private static final int DATABASE_VERSION = 1;
    
    // Table information
    private static final String TABLE_NAME = "products";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_NAME = "name";
    private static final String COLUMN_PRICE = "price"; // This column will store float values

    // Create table query
    private static final String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + "(" +
            COLUMN_ID + " INTEGER PRIMARY KEY," +
            COLUMN_NAME + " TEXT," +
            COLUMN_PRICE + " REAL" +
            ")";

    public MyDatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Handle database schema changes if needed
    }

    // Method to insert a product with price (float)
    public void insertProduct(String name, float price) {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_NAME, name);
        values.put(COLUMN_PRICE, price + "f"); // Ensure float value with 'f' suffix

        db.insertOrThrow(TABLE_NAME, null, values);
        db.close();
    }
}

Explanation:

1. This code defines a helper class MyDatabaseHelper that extends SQLiteOpenHelper to manage the database creation and upgrades.
2. It defines constants for database name, version, table name, and column names.
3. The CREATE_TABLE query defines the table structure with an id (primary key), name (text), and price (REAL) column.
4. The insertProduct method takes a product name and price as arguments.
5. It gets a writable database, creates a ContentValues object, and adds the name and price (with "f" suffix) using put methods.
6. Finally, it inserts the data using insertOrThrow and closes the database connection.

• You can convert the double or float value to a String using String.valueOf(yourDoubleValue).
• Insert this String value into a column defined with the TEXT storage class.

Consideration:

• This method might lead to a loss of precision, especially for long decimal values.
• Retrieving the data later would require converting the String back to a double/float, which might introduce additional rounding errors.

Using BigDecimal Class:

• The BigDecimal class in Java provides arbitrary-precision decimal arithmetic.
• Convert your double or float value to a BigDecimal using its constructor.
• Store the BigDecimal object as a String in a TEXT column (similar to the previous method).

• This method offers higher precision compared to storing as plain text.
• It requires additional processing for conversion and retrieval (converting BigDecimal to String and vice versa).
• This approach might be less efficient for large datasets due to the overhead of BigDecimal operations.

In summary:

• Use the REAL storage class for most cases involving double and float values in SQLite for Android.
• If you absolutely need the highest precision and are dealing with financial calculations, consider using BigDecimal.
• Avoid storing floating-point values directly as text unless precision loss is acceptable.