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The Use NZ For Access And Null Values

The Use NZ For Access And Null Values

NZ(me.thisfieldhasnovalue,”Evaluating Nulls”)

Using NZ does ONE evaluation step which gets the data you requested from a field or formula (if it is NOT null), otherwise it will pass in a new value to use in it’s place so the formula or expression does not break due to a NULL.  This is required in a lot of scenarios due to the fact you can not evaluate “nothing” to determine a required outcome.

examples:

if nz(me.fname,0) <> 0 then

    msgbox “Hello ” & fname

else

    msgbox “You do not have a first name”.

end if

or another example I would use in a group by query for product sales,

this would be the query column formula:

NewItemCost: nz(me.itemcost,0))

In the last example if itemcost was left blank the sum formula would have failed because you can’t sum NULL plus values.  but you CAN sum 0 plus values.  So now I can do a group by on this query, or a sum on that new field I created.  Without the NZ I can not.  The real problem is allowing NULLS on a cost field.  one should default in 0 and force a value in the property of the field on the form, by using a validation setting of “Is Not Null”.  You can also do defaults at the table level, but I rarely endorse that .  I like all formulas and defaults and settings done at forms, unless it is the primary key, a timestamp, or a bit field.  once in a while I default values for number or text fields on tables, but I find this permanently binding so I prefer to do the default at a form level.

Happy databasing!

Follow me on twitter if you aren’t already!   @jhshirley

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