data hierarchy A hierarchical structure of records, in which (a) a record at level i holds data that is common to a set of records at level i + 1 and (b) starting from the higher-level record, it is possible to access the set of lower-level records. Any record may only “own” one set of lower-level records, and may only be a member of one such set. A data hierarchy may reflect “real-world” hierarchical relationships, or may be a user view provided by a DBMS to facilitate a purpose or activity.
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