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Use Delegation to Share Implementation
The delegation "Delegation comprises of catching an operation on one object and sending it to other object which is part, or related to first object. In this method, only meaningful operations are delegated to second object, and meaningless operations can be banned from being inherited accidentally".
It is actuality that inheritance is an event for implementing generalization, in which behaviour of super class is shared by all of its subclasses. But, sharing of behaviour is justifiable only when a true generalization relationship come across, that is, only when it can be said which subclass is a form of the super class.
What is Foreign Key Foreign Key: Sometimes we may have to work with an attribute that does not have a primary key of its own. To recognize its rows, we have to use the primar
If the deletion violates referential integrity constraint, then three alternatives are available: Default option: - refuse the deletion. It is the job of the DBMS to describ
Creating views with check option : This option limits those updates of data values that cause records to go off the view. The following instance tells this in more detail: Examp
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Define Shared locks? Ans: Shared lock: Throughout concurrent execution of transactions, earlier than a transaction can access a data item, it has to obtain a lock on it. Now he
Security: Data not needed by local applications is not stored at the site, therefore no unnecessary security violations may exist. But how can we carry out fragmentation? Fragm
Describe the types of Inheritance 1. Single inheritance 2. Multiple inheritance 3. Hierarchical inheritance 4. Multilevel inheritance
Let us first look into some of the important features of ER model. Entity relationship model is a high-level conceptual data model. It permits us to define the data invo
Write short notes on relational constraints? Relational Constraints are: 1. NOT NULL 2. Unique 3. Primary key 4. Foreign key 5. Table check
FDs in Entities : Student entity : Enrolment number → Student name, Address Course Entity :
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