Propagation constraint: Difference between revisions

Revision as of 09:44, 26 May 2005

Revision as of 02:10, 11 October 2005

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According to Beynon-Davies (2004, p.108) "''[a] propagation constaint 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[[relationship]]s, one should define how to handle deletions of target and related tuples[[tuple]]s. There are three possibilities:

* Restricted Delete - cannot delete the target row until all rows that point to it (via [[foreign keyskey]]s) have been deleted.

* Cascades Delete - can delete the target row and all rows that point to it (via foreign keys) are also deleted.

* Nullifies Delete - can delete the target row and all foreign keys (pointing to it) are set to [[null]].

Beynon-Davies, P. (2004) ''Database Systems'' Third Edition, Palgrave.

[[Category:Data modeling]]