A variable of RECORD type can contain fields of another RECORD type or any collection type. All collections and RECORD types can be defined in PL/SQL blocks, packages, or at the schema level. Unlike nested tables and associative arrays, varrays can contain elements of RECORD type, and collections can be both sparse and dense. Additionally, not all collections and RECORD types can be stored in table columns, and they do not always have default values of null except in specific circumstances.