Query gives blank result in some rows

[captnk]

I have a query made from 2 tables.
4 of the fields are joined.
When I run the query provided all tables have a value/text,the correct answer is given
HOWEVER if in any of rows of the joined fields their is no value/text (null) in any 1 or more of the fields,then a zero answer results.
Each field is an identifying item to give the correct result.In some cases all fields r needed to identify the correct product,in other cases 1 field is all thats needed.
Please can someone identify what I need to do to get the query to find on any or all of the rows
Thanks

 

[edtab]

Try getting rid of your "null" values.
You can do this by creating an "update query" and assigning a value of "0" (zero) to all number fields containing "nulls".

 

[captnk]

Thanx
I had tried using null value insertion,but that didnt seem to work.
Why I dont know
1 column is the main,and the others are all sorts of sub classes.
I have sort of in a long winded way overcome some of the problem,by running about 8 different queries on each variation,and appending them to a single table,
but it is longwinded and very unsatisfactory.
So the mystry remains