vba understanding (97nl)

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Hello all,

Could someone tell me why example 1 does not work and example 2 will work:

example 1
———————————–
If numPrio = 0 Then
If datD1 = Null Then
datDeadline = datHD
Else
datDeadline = datD1
End If
Else
datDeadline = datD2
End If
———————————–

example 2
———————————–
If numPrio = 0 And datD1 = Null Then datDeadline = datHD
If numPrio = 0 And datD1 = Null Then datDeadline = datD1
If numPrio 0 Then datDeadline = datD2
———————————–

They seem the same to me, but they word different
Thanks in advance.

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Perhaps you didn’t copy Example 2 correctly: it contains “If numPrio = 0 And datD1 = Null Then” twice.

In fact, both code samples are incorrect. You cannot compare a value to Null by testing “If … = Null Then”, since Null is not really a value, it indicates the lack of a value. Use the IsNull function instead:

If NumPrio = 0 Then
If IsNull(datD1) Then
datDeadline = datHD
Else
datDeadline = datD1
End If
Else
datHeadline = datD2
End If

Even shorter is the use of the Access-specific Nz function:

If NumPrio = 0 Then
datDeadline = Nz(datD1, datHD)
Else
datHeadline = datD2
End If

Nz returrns the first argument, unless that is Null, then it returns the second argument.

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Great Hans,

Thanks, I understand the problem now

Reply | Quote

Great Hans,

Thanks, I understand the problem now

Reply | Quote

Perhaps you didn’t copy Example 2 correctly: it contains “If numPrio = 0 And datD1 = Null Then” twice.

In fact, both code samples are incorrect. You cannot compare a value to Null by testing “If … = Null Then”, since Null is not really a value, it indicates the lack of a value. Use the IsNull function instead:

If NumPrio = 0 Then
If IsNull(datD1) Then
datDeadline = datHD
Else
datDeadline = datD1
End If
Else
datHeadline = datD2
End If

Even shorter is the use of the Access-specific Nz function:

If NumPrio = 0 Then
datDeadline = Nz(datD1, datHD)
Else
datHeadline = datD2
End If

Nz returrns the first argument, unless that is Null, then it returns the second argument.

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