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ntmartins
New User
Joined: 03 Mar 2008
Posts: 11
Location: Lisboa, Portugal
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| The zoo has a business rule that a food cannot be deleted if that food is the only food eaten by any animal. Can this rule be enforced by referential integrity (foreign key) constraints? (In other words, can referential integrity keep us from deleting a food from LEGAL_FOOD if that food occurs in the only species-food row for a particular species?) |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006
Posts: 19243
Location: Inside the Matrix
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Hello,
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| can referential integrity keep us from deleting a food from LEGAL_FOOD if that food occurs in the only species-food row for a particular species |
I believe not. Referential integrity could prevent deletion if this food was eaten by some animal, but not if it is the only food eaten by an animal.
The deletion validation would go something like determining a list of animals who ate this food, then determining if this food was the only food eaten by each animal in the list. Not a feature/function of referential integrity. |
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Craq Giegerich
Senior Member
Joined: 19 May 2007
Posts: 1512
Location: Virginia, USA
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| I think it could be enforced by a trigger. |
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