> As soon as fake value becomes normal business value problems might > arise. I'd personally better deall with NULLs because this is > WIDELY understand concept both by developers and DBMSes compared > to some specific value representing NULL, which is -1 for project1, > 0 for project2 and 187913267532 for project3. I agree. When I do data modeling, I personally never use a fake value for a simple missing value (as for reason of avoiding outer joins). But if multiple special values are needed in the design, and the developers agree, I could use e.g. -1 for generally unknown, -2 for lost, -3 for ... In this case, a single NULL couldn't satisfy the business need, and an additional column for these special values would be a little too wasteful. Yong Huang -- //www.freelists.org/webpage/oracle-l