Object-Relatinal Mismatches

Object-Relatinal Mismatches Encapsulation Object-oriented programs are designed with methods that result in encapsulated objects whose representation is hidden. Mapping such private object representation to database tables makes such databases fragile according to OOP (object-oriented programming) philosophy, since there are much fewer constraints for design of encapsulated private representation of objects compared to a database’s use of public Read more about Object-Relatinal Mismatches[…]

Surrogate Key VS Natural Key

Surrogate Key: Surrogate keys are keys that have no “business” meaning and are solely used to find a record in the table.  Such keys are either database generated (example: Identity in SQL Server, Sequence in Oracle, Sequence/Identity in DB2 UDB etc.) Natural Key:  Keys are natural if the attribute it represents is used for identification independently of Read more about Surrogate Key VS Natural Key[…]

Aggregation Vs Composition

Aggregation Aggregation is a form of association in which one element consists of other, smaller constituents. This relationship is depicted by a diamond-shaped white arrowhead. In this case, if the parent object is deleted, the child object may still continue to exist. Figure 12 shows an aggregation relation between an insurance agent and the local insurance Read more about Aggregation Vs Composition[…]