if table1.field1 is empty, table2.field1, table1.field1 in form

[ricardozelaya via AccessMonster.com]

I'm trying to select where to get the data from in a form. I have two tables,
one or both of them contain the information. I want the form to be filled
with data from table 1, but if table 1 does not contain data, I want to get
it from table 2. I put the following in the control source:
=IIF(table1.field1=null, table2.field1, table1.field1)

How am I supposed to write that expression?

Thanks

 

[Douglas J Steele]

You cannot use = in conjunction with Null: you must use the IsNull function:

=IIF(IsNull(table1.field1), table2.field1, table1.field1)

Another, perhaps simpler, alternative is:

=Nz(table1.field1, table2.field1)