# Formula to handle null vs not null

Field A is a number field and some records have a null value.
Field B is a number filed and the records have no null values.

I need a formula for a new field "C" that places that does an IF kind of thing

IF Field A is not null, THEN put "A - (whatever the number in Field A is)" in Field C
Otherwise, put "B - (whatever the number in Field B is)" in Field C.
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Commented:
In field C you can use:
=IIF(isnull([FIELD_A]), [FIELD_B], [FIELD_A])

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Owner, Developing Solutions LLCCommented:
First, I would recommend against filling in a field with a computed value based on these other two fields.  Unless you have a data macro which will automatically update [FieldC] every time a change is made in [FieldA] or [FieldB], you are far better off computing the value that would be [FieldC] every time you need that value (in a query).

Not quite sure I understand your logic.  Won't the following always equal zero:

A - (whatever the number in Field A is)
B - (whatever the number in Field B is)

To add or subtract values that may contain NULLS, you should use the NZ function to convert the value to a zero before performing arithmetic, something like:

FieldC: NZ([FieldA], 0) + NZ([FieldB], 0)
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