Nonmaterialized columns exist virtually, but are not physically stored in the row. Use nonmaterialized columns the same as any other column, selecting, updating, and referring to them in SQL queries, or using them as index keys.
Adaptive Server treats nonmaterialized columns the same way
it treats null columns: if a column is not physically present in
the row, Adaptive Server supplies a default. The default for a nullable
column is null, but the
default for a nonmaterialized column is a user-defined non-NULL
value.
Converting a nonmaterialized column to a physically present column is called “instantiating” the column.
