HCL Informix® supports
nested collections as a column type. A nested collection is a collection column
whose element type is another collection. For example, the code fragment
in the following figure creates the tab_setlist table whose
column is a nested collection. Figure 1. Sample column with nested collection
EXEC SQL create table tab_setlist
( setlist_col set(list(integer not null));
The setlist_col column is a set, each element
of which is a list. This nested collection resembles a two-dimensional
array with a y-axis of set elements and an x-axis of list elements.