I'm trying to join together five columns under one column heading when querying a table;

SELECT ([DD].[DADDR1] + [DD].[DADDR2] + [DD].[DADDR3] + [DD].[DADDR4] + [DD].[DADDR5]) AS 'DELIVERYADDRESS'
FROM DELDETS DD
WHERE DD.DRECNO=274001

However, whenever this query is run I get a null value returned - yet the query when run to return the five columns (i.e. SELECT DD.DADDR1, DD.DADDR2, DD.DADDR3 ...) does return data. It would seem that concatenating more than two columns in T-SQL is not possible - does anyone know if this is indeed the case?

Your syntax is fine, but if any of the columns contain a null value then the whole concatenated value will be null.

Use COALESCE to change any nulls to empty strings
SELECT (COALESCE([DD].[DADDR1], '') + COALESCE([DD].[DADDR2], '') + etc

Fantastic, working great now. Thanks!