使用SQL查询的输出填充DataTable中的列

Question

I have a DataTable with this structure:

number   amount    destroyed    together
     1       19            3          22
     2       20            3          23
     3       11            0          11

The value in the destroyed column is manually inserted by the user. However, I've created a table in SQL where a user can add a value for destroyed and I want to take the value from this table. I already have the proper SQL query for this.

The following example will demonstrate.

Here is output from the query :

number    destroyed     type
     1            3   papper
     2            1   papper

According to the structure of the DataTable it should insert a value for destroyed from this SQL query into DataTable when

Query.number = DataTable.Number

So according to this example it should look like:

number   amount    destroyed    together
     1       19            3          22
     2       20            1          21
     3       11            0          11

How do I accomplish this?

Answer 1

You haven't posted how you're connecting and executing your SQL statement. Using SqlConnection and friends to execute a statement:

// For each row in the DataTable...
for (int i = 0; i < dataTable.Rows.Count; i++) {
    // Get record where number equals the DataTable's "number" column for this row
    // Then select the destroyed value:
    string sql = String.Format("SELECT * FROM Table WHERE number='{0}' THEN destroyed", dataTable.Rows[i]["number"].ToString());
    int destroyedCount = 0;

    // Execute the SQL query, return value to `destroyedCount`
    using (SqlConnection conn = new SqlConnection(connString))
    {
        SqlCommand cmd = new SqlCommand(sql);
        try 
        {
            conn.Open();
            destroyedCount = (int)cmd.ExecuteScalar();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }

    // Set the table value to the SQL command's returned value
    dataTable.Rows[i]["destroyed"] = destroyedCount;

    // Assuming you want amount + destroyed = together
    int amountCount = 0;

    // Parse the table's current value for `amount`
    try 
    {
        amountCount = (int)dataTable.Rows[i]["amount"];
    }
    catch (ArgumentNullException argEx)
    {
        // Handle exception
    }
    catch (FormatException formatEx)
    {
        // Handle exception
    }

    // Set the `together` column to `amount` + `destroyed`
    dataTable.Rows[i]["together"] = (amountCount + destroyedCount).ToString();
}