Checking If Yes/No Field Is Null

[DMT Dave]

Hi Guy's What is the method of checking if yes/no field is null

is it
if = 0
if is null


if = nothing

???

 curTotal = DSum("Price", "tblInvoices", "[Customer] = '" & strCust & "'")            curPaid = DSum("Price", "tblInvoices", "[Customer] = '" & strCust & "' And Paid = Yes")
            
            If curUnpaid = DSum("Price", "tblInvoices", "[Customer] = '" & strCust & "' And Paid = No") = 0 Then
            curUnpaid = "00.00"
            Else
            curUnpaid = DSum("Price", "tblInvoices", "[Customer] = '" & strCust & "' And Paid = No")
            End If

[June7]

A yes/no data type field is never null. It is either -1 or 0.

[DMT Dave]

Thanks June7 so would i remove the where i have highlighted red and change

and Paid = 0 instead of No ?

[ranman256]

in a query:
where [field] is null


in forms:
if IsNull(txtBox) then

but yes, boolean fields are not null.

[DMT Dave]

Got it June7, thank you, changed to If Is Null, this appeared to have worked ok

If IsNull(curUnpaid = DSum("Price", "tblInvoices", "[Customer] = '" & strCust & "' And Paid = No")) Then            curUnpaid = "00.00"
            Else
            curUnpaid = DSum("Price", "tblInvoices", "[Customer] = '" & strCust & "' And Paid = No")End If

[June7]

Simplify, eliminate the If Then and the repeated DSum:

curUnpaid = Nz(DSum("Price", "tblInvoices", "[Customer] = '" & strCust & "' And Paid = No"), 0)

Why would you set curUnpaid to a string? Instead of using Customer why not the Customer ID?

[Micron]

perhaps review
http://allenbrowne.com/NoYesNo.html