Decimal values being rounded in Sqlite

Question

After migrating my database from Access to Sqlite 3 in a Windows Forms application, I have been having difficulties with Decimal values. If I run a simple select:

SELECT * FROM Item WHERE id = 1;

The decimal values of the preco_item column are correctly displayed, with 2 decimal places. Example: 2.53 = 2.53. But when I do a query a little more complex, with related tables as following:

SELECT Produto.nome AS Produto, 
                Item.quantidade AS Quantidade, 
                Item.preco_item AS Preço,     
                Item.preco_item * Item.quantidade as Subtotal,               
                Item.id  
            FROM Item  
            INNER JOIN Orcamento ON Item.id_orcam = Orcamento.id   
            INNER JOIN Produto ON Item.id_produto = Produto.id   
            WHERE(Orcamento.id = 1 );

The results obtained in the Price line are presented in DataTable thus: 2,53 = 2,00, thus also happens with the result of multiplication preco_item * quantidade.

Note: Monetary items are set to Decimal(7.2) in Sqlite. I have tried several other formats. In the query by Sqlite Studio, the price results present normally, with the exception of multiplication that I have not yet found a way to calculate correctly. Always returns an integer value to me.

P.S.: Values are entered into a Datagridview via Datatable.

Update to demonstrate BD schema:

private static string createQuery()
{
        string createScript = "CREATE TABLE Cliente (" +
            " id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
            " nome       TEXT NOT NULL UNIQUE," +
            " endereco   TEXT," +
            " local      TEXT," +
            " telefone_1 TEXT," +
            " telefone_2 TEXT ); ";
        createScript += "CREATE TABLE Produto (" +
             " id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
             " nome  TEXT NOT NULL UNIQUE," +
             " preco DECIMAL ); ";
        createScript += "CREATE TABLE Tipo (" + 
            " id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,"  + 
            " nome      TEXT," + 
            " descricao TEXT ); ";
        createScript += "CREATE TABLE Orcamento (" +
            " id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT," +
            " id_cliente INTEGER REFERENCES Cliente (id)," +
            " data DATETIME," +
            " id_tipo INTEGER REFERENCES Tipo(id)," +
            " desconto DECIMAL," +
            " status TEXT DEFAULT Pendente ); ";
        createScript += "CREATE TABLE Item (" +
            " id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
            " id_orcam INTEGER REFERENCES Orcamento (id)," + 
            " id_produto INTEGER REFERENCES Produto(id)," +
            " preco_item DECIMAL," + 
            " quantidade INTEGER NOT NULL ); ";

        return createScript;
}

Here is the code that fills the Datagridview:

string query = Queries.GetItemsByOrcId(orcId);
sql.CustomSelect(query);
dgvpProd.DataSource = sql.Datatable;

Answer 1

I have found a solution based on the suggestions of colleagues. The monetary value fields were created as INTEGER and I treated the entire decimal formatting via code in the application. The class structure that I created allowed me to convert the values into Datatable before arriving at the application dataGridview. Follows the main method of the class:

public static DataTable dtColumnIntToDecimal(DataTable dt, int column)
    {
        List<decimal> price = new List<decimal>();
        //Gerar lista de valores em decimal
        foreach (DataRow row in dt.Rows)
        {                
            decimal aux = Convert.ToDecimal((long)row[column]) / 100;
            price.Add(aux);     
        }

        //clonar o datatable, transformando a coluna em decimal
        DataTable dtCloned = dt.Clone();
        dtCloned.Columns[column].DataType = typeof(decimal);
        foreach (DataRow row in dt.Rows)
        {
            dtCloned.ImportRow(row);
        }

        //Inserir valores em decimal
        for (int rowIndex = 0; rowIndex < dt.Rows.Count; rowIndex++)
        {
            dtCloned.Rows[rowIndex][column] = price[rowIndex];
            Console.WriteLine(dtCloned.Rows[rowIndex][column]);
        }

        //atualiza o total de valores (opcional) 
        valorTotal = price.Sum();
        //Retorna o DataTable
        return dtCloned;
    }

Code for use of class:

//Minha consulta
sql.Select("Produto", tbConsulta.Text);                        
//DataTable retornado
DataTable dt = Util.dtColumnIntToDecimal(sql.Datatable, 2);
//Aplicação do DataTable ao DataGridView
dataGridView1.DataSource = dt;

... and for the currency format to appear correctly without deleting the zeroes after the comma, just apply the "C2" in Defaultcellstyle.Format in the column.