Question

I’m writing a front end to a database, presenting options as comboboxes. And I need to be able to return nulls to the database.

I have a solution at the moment which involves ‘fudging’ a record into the query to populate the Datatable, then detecting the selection and hard coding null into my update statement if this item has been selected.

--GetDataByAvailableTechs query              SELECT     tblLEMSCredentialsId, TechNumber             FROM         tblLEMSCredentials AS aLEMSCreds             UNION ALL             SELECT     '99999' AS Expr1, '<NONE>' AS Expr2 

.

            //populate combo box             BV_LEMSHIPDataSet.tblLEMSCredentialsDataTable dtAvailableTechs = taLEMSCreds.GetDataByAvailableTechs(selectedSerial);               cboTechNumber.DataSource = dtAvailableTechs; 

.

            //Save back to DB             if (lemsCredsID == 99999)             {                 taDevice.UpdateQuery_Restage(null, selectedSerial);             }             else             {                 taDevice.UpdateQuery_Restage(lemsCredsID, selectedSerial);             } 

Can anyone suggest a better way of doing this please? I need to make the application cope with another 5 similar fields and don’t want to create a multitude of if else versions of my update.

G

Answer 1

In the past I’ve used a similar approach but used minus numbers for the NULL values – that way you can you treat anything less than zero as NULL in one if statement.

This assumes that your ID’s in the table are always positive though 🙂