BCS3473 OOADD : Chapter 18 - Data Management Design

Chapter 18 - Data Management Design

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Exercise

1.  What are criteria for a table design to be in:-

                          

                              i.    First Normal Form (1NF), how do you convert a normalized design to 1NF?

                            ii.    Second Normal Form (2NF), how do you convert 1NF design to 2NF design?

                           iii.    Third Normal Form (3NF), how do you convert 2NF design to 3NF design?

i.        A record is said to be in first normal form if it contains no repeating groups. To convert an unnormalized record you would expand the primary key of the record to include the key of the repeating group.

ii. To be in second normal form, a record must first be in first normal form and all fields that are not part of the primary key must be dependent on the entire primary key. To convert from 1NF to 2NF, you would create a new record for each field and a possible combination of the fields in the primary key. For each new record, designate one field or combination of fields as a primary key. Place the remaining fields with the primary key on which they depend. When finished placing the fields, discard any record that does not contain any additional fields other than its primary key. The remaining records are the 2NF of the original record.

iii. A record is in third normal form if it is in second normal form and if no nonkey field is dependent on another nonkey field. To convert a record to 3NF you would move the dependent field to a new record, which has the field it is dependent on as the primary key.

18.1  Give one example each of persistent object and transient object.

18.4 Outline the advantages and disadvantages of using a database management system over developing an application using files.

18.5 What is the key differences between a relational DBMS and object DBMS?