This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: can RELATIONSHIP at most how many instances of ENTITY2's Or: each CUSTOMER can ORDER Exercises o Order - has - item You can have multiple items on one order A bag of flour can be on more than one order (a vehicle by vin # could not be on more than one order however o Item - supplied by - supplier What's the problem with M:M relationships? o Really confusing! o Create a linking table Always use singular when naming a table and working with these. Mapping o Sequence Map entities Map relationships 1:M 1:1 M:M o For 1:M The primary key in the 1 side becomes the foreign key on the many side o For 1:1 Check to see if there's an optional side The primary key on the required side becomes the foreign key in the optional side...
View Full Document
This document was uploaded on 04/04/2011.
- Winter '09