Propagation constraint
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Propagation constraint in a relational database refers 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 tuples. There are three possibilities:
- Restricted Delete - cannot delete the target row until all rows that point to it (via foreign keys) 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.
[edit] Bibliography
- Beynon-Davies, P. (2004) Database Systems Third Edition, Palgrave.
