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Propagation constraint in a [[relational database]] referes to how consistency is maintained between coupled tables. According to [[Beynon-Davies]] (2004, p.108) "''[a] propagation constraint details what should happen to a related table when we update a row or rows of a target table''". He further states that for all relationships, one should define how to handle deletions of target and related [[tuple]]s. There are three possibilities:
* Restricted Delete - cannot delete the target row until all rows that point to it (via [[foreign key]]s) have been deleted.
* Cascades Delete - can delete the target row and all rows that point to it (via foreign keys) are also deleted.
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