Help with code

[Guest]

Hi

I have this on current event running ok...but I need to add something for X1
below.
I do not want to set X3 = true if X1 = Null
So I need two conditions in the same "if".

Private Sub Form_Current()
If Me!X1 = Me!X2 Then
Me!X3 = True
End If
End Sub


Thank you in advance

Mattias

 

[Marshall Barton]

I have this on current event running ok...but I need to add something for X1
below.
I do not want to set X3 = true if X1 = Null
So I need two conditions in the same "if".

Private Sub Form_Current()
If Me!X1 = Me!X2 Then
Me!X3 = True
End If
End Sub

You won't set X3 if X1 is Null, even if X2 is also Null.
The If can not possibly succeed when either value is Null,
because Null represents a value of "unknown" and nothing is
ever equal to "unknown".

If you should need to check if something is Null, use the
IsNull function.

 

[Brendan Reynolds]

Well, if X1 is Null, your condition will never evaluate to True, even if X2
is also Null, because the expression Null = Null evaluates as Null. So your
existing test already excludes the condition where X1 is Null.

More generally, though, you can test multiple conditions in an If statement
like so ...

If (A = B) And (B <> C) Then ...

To check for Null values, don't use the = operator, use the IsNull function
....

If (A = B) And (Not IsNull(C)) Then ...

This stuff become easier to understand if you keep in mind that Null
represents an unknown value. Is one unknown value equal to another known or
unknown value? The answer is unknown, i.e., Null. Similarly, what is the
value of a known number multiplied by an unknown number? Again, the answer
is unknown, i.e., Null.

--
Brendan Reynolds (MVP)
http://brenreyn.blogspot.com

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