How to hold a SQL SUM() query int a Variable

Question

Good day. I have an SQL query in C# as shown.

using (SQLiteConnection con = new SQLiteConnection(Connection.DatabaseLocationString))
        {
        SQLiteCommand cmd = null;
        string query = 
               String.Format("SELECT  MONTH(SaleDate)  month,
                              SUM(AmountPaid)  sum_amountpaid   
                              FROM {0} 
                              WHERE YEAR(SaleDate) = @1  
                              GROUP BY  MONTH(SaleDate)  ", Sale.TABLE_NAME);
        cmd = new SQLiteCommand(query, con);
        cmd.Parameters.Add(
                  new SQLiteParameter("@1", Properties.Settings.Default.ChartYearlyDisplay));
        con.Open();
        SQLiteDataReader reader = cmd.ExecuteReader();

        con.Close();
        }

My challenge is, i have never done nor used a query like this. But what i want to achieve is, i want too Get the value of SUM(AmountPaid) for each month, like this.

• January = 20000.00
• Febuary = 18000.00
• March = 10000.00 .......and so on.

But i really dont know how too come of that. please i need your help, Thanks.

Answer 1

You just need to loop over the returned results using the SQLiteDataReader

SQLiteDataReader reader = cmd.ExecuteReader();
while(reader.Read())
{
    Console.WriteLine(reader["month"].ToString());
    Console.WriteLine(reader["sum_amountpaid"].ToString());
}
con.Close();

Of course, if you need to return this data, you need a data structure where you can store the results like a List<T>

// The class where you keep the value for a single month...
public class MonthAmount
{
    public int Month {get;set;}
    public decimal Amount {get;set;}
}
....

// A List where each month of data will be added...
List<MonthAmount> amountData = new List<MonthAmount>();

while(reader.Read())
{
    // Create the instance of MonthAmount for the current month..
    MonthAmount m = new MonthAmount()
    {
          Month = Convert.ToInt32(reader["month"]); 
          Amount = Convert.ToDecimal(reader["sum_amountpaid"]);
    }
    // Add it to the list...
    amountData.Add(m);
}
reader.Close();
// Return the info to the caller....
return amountData;

Also according to SQLite docs , there is no MONTH or YEAR functions available, you should use strftime with an appropriate settings. You could try with

string query = $"SELECT  strftime('%', SaleDate)  month,  
                 SUM(AmountPaid)  sum_amountpaid   
                 FROM {Sale.TABLE_NAME}    
                 WHERE strftime('%Y', SaleDate) = @1  
                 GROUP BY strftime('%m', SaleDate)";

And if I am not wrong, the result of this strftime function is a string not an integer (IE '03' for March, '2017' for year) so perhaps you should create a parameter with the correct datatype.