Add a collection type to an existing table
You can use the ALTER TABLE statement to add or drop a
column that is a collection type (or any other data type). For example,
the following statement adds the flowers column, which is defined
as a SET, to the nursery table:
ALTER TABLE nursery ADD flower SET(VARCHAR(30) NOT NULL)
You cannot modify an existing column that is a collection type or convert a non-collection type column into a collection type.
For more information about adding and dropping collection-type columns, see the ALTER TABLE statement in the Informix® Guide to SQL: Syntax.