How do you not return records in a query if those records have the same value in a field?

For example the following records are sorted so that the "x" field is unique

x y
A X
A Y
B Z
B X

Sorted gives:
x
A
B

Add field1 to the field grid in design view
Right click on the field grid and turn on Totals.

A row will appear showing GROUP BY.

Job done.

I only want to group by one field, and it wont let me do that.