Concatenating Strings
When IBM® Cognos® Business Intelligence
concatenates strings locally and if any of the involved strings contain
null values, the result of the concatenation is an empty cell or a
null value. This occurs because IBM Cognos BI requires that an expression
that involves a null value returns a null value. Many databases ignore
null strings when they perform concatenations. For example, if you
concatenate strings A, B, and C, and if string B is a null value,
the database may concatenate only strings A and C.