Query Containing Iif Statement - Scope Issue

I've come across an issue today that I didn't think was possible in Access or it's possible I've not met these conditions before..

A field containing an if statement in a query is brought into another query. The iif statement then appears to be working within the top query as well, when I am just expecting to display the results of the initial query.

I've struggled to describe this clearly, this is my best attempt so far.

For example

I have a query (Q1) returning 3 rows, the first field is a unique field, the second field is an optional field, the third field is an if statement. eg iif [field 2] is null Then "default" Else [field 2]

Output should be 3 rows: Default value = "No response"

Field 1___________Field 2__________Field 3

1________________Yes____________Yes
2_______________________________No response
4________________No_____________No



I am then joining Q1 to a table (T1) with 6 rows and one field, the unique field.

I want all 6 from T1 and matching rows from Q1.

I am expecting to see this result.


T1.Field 1_________Q1.Field 2_______Q1.Field 3

1________________Yes____________Yes
2_______________________________No response
3
4________________No_____________No
5
6


However, I am getting

T1.Field 1_________Q1.Field 2_______Q1.Field 3

1________________Yes____________Yes
2_______________________________No response
3_______________________________No response
4________________No_____________No
5_______________________________No response
6_______________________________No response

You can see that Q1.Field 3 is now returning a default value for the rows that aren't actually in Q1.

The iif statement is working on the larger dataset when I want, expected it to only work within Q1.


Phew, I hope someone can make sense of that and secondly help me out.

Is it supposed to work like this? (I don't think so)
How do I stop it working like this? - I have made the result of Q1 into a table and linked that to T1, giving me the right answer. However, I just can't believe this is correct as it would stop you using a query within a query.

Thanks in Advance.