Combo Box with duplicate data

Question

Hello All,
I am creating a form with a combo box but the data from the table is duplicating.  Can anyone provide guidance on how to make the combo box only display only two choices of the data?  For example, when the box is selected the drop down list
will have multiple/group of  'Yes' and 'No'.  It appears that everytime a record is added to the table, it gets duplicated.  I think I'm overlooking something from working long on this and it maybe something simple/obvious.   Any
help would be appreciated, thanks.
Evin

Answer 1

As Bruce said you can use the DISTINCT predicate to suppress duplicate rows, but if you are getting duplicates in a combo box's list it suggests that you are querying the wrong table as the Control's RowSource property.  If we take a simple example
of a combo box to list states, then the following would return duplicates of the table contains rows for two or more cities in the same state:
SELECT State
FROM Cities
ORDER BY State;
You could suppress the duplicates with:
SELECT DISTINCT State
FROM Cities
ORDER BY State;
but the correct solution would be:
SELECT State
FROM States
ORDER BY State;
i.e.  in the Cities table State is a foreign key column referencing the primary key of States.  You might ask why have a States table at all as the values are already in Cities?  The answer is that by having a States table you can enforce referential
integrity in the relationship between Cities and States, preventing the insertion of invalid State values into Cities.  Without protecting the integrity of the database in this way errors in data entry will sooner or later occur (Murphy's Law is infallible
in this respect!).  I have personal experience which is testament to this, having once found three versions of my own name as author in a table of references to technical articles in my own field of work.  As far as the database is concerned this
makes me three separate people!  The table should have referenced the key of an Authors table of course.
Ken Sheridan, Stafford, England