Wiley 978-0-7645-7677-5 Datenblatt

Introduction to MappingObjects to RelationalDatabasesIn the computer industry, we commonly have discussions, disagreements, and even shoutingmatches o

newFeatures and count columns need to be populated with a value such as null. But will this work?Can’t we have a SpecialEditionCD object where both th

created. Maintaining these relationships can be complex, depending on the hierarchy being mapped. Wearen’t wasting database space if we have a CD obje

To map the relationship shown in Figure 1.5 to a relational database, we need to use a foreign key thatassociates the owner with the account. Since th

Figure 1.6As you can see, the foreign key, account_id, is used in the mapping just as it is in the one-to-one rela-tionship map. When an account is ad

14Chapter 1cost int,accounts int);create table account_security (ID int not null primary key auto_increment,account_id int,security_id int,);Figure 1.

SerializationYou can save data stored in an object by creating a flat-file representation of the object. In the Java lan-guage, this process is called

create table cd (title varchar,artist varchar);From the XML, we can easily build a class like this:public class cd {String title;String artist;}Having

class has two attributes that would need to be mapped to a relational database table for permanent stor-age. The title and artist fields can be mapped

ArrayList tracks;public CD(String title, String artist) { this.title = title;this.artist = artist;tracks = new ArrayListO;}public void addTrack(String

If we have another CD to store, should another track table be added to the system, or should the tracksbe added to the existing CD_tracks table? If we

Our CD class can be further complicated by adding an attribute based on another class type. For example:public class CD implements Serializable { Stri

Primary Keys, Timestamps, and Version NumbersIn the examples presented so far, all the database tables have included a primary key that isn’t part oft

❑ Create a single table using the attributes from the lowest child.❑ Create a table per class.❑ Create a table per concrete class.Let’s consider each