Question

I am working on a project with MS Access 2010.

A person with an illness needs to matched against two people without the illness, or controls. These two controls need to be the nearest in terms of age as possible.

I have matched suitable controls but I am struggling to make a query to select just the two controls with nearest dates of birth (Date difference) to the people with the disease.

(The date_difference field is an absolute number so even if they are younger or older the number is always positive – obviously, a higher number indicates they are more years apart).

Can anyone help?

For example… (obviously all names are completely made up!)

For example…

I would like the outcome of a query to generate the following:

output

Any help will be MUCH appreciated!

James

Answer 1

I hope the whole table set-up is imaginary.

SELECT b.id,
       b.disease_id,
       b.disease_surname,
       b.control_id,
       b.control_surname,
       b.date_difference
FROM   controls AS b
WHERE  b.id IN (SELECT TOP 2 id
                FROM   controls a
                WHERE  a.disease_id = b.disease_id
                ORDER  BY date_difference)