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Explain what is Aggregation ?
Aggregation: This is used whenever we intend to show a relationship between an entity and the relationship. There is no provision for this in the ER Model. This is shown by placing the relationship between two entities along with the entities in a box and setting up a relationship between this box and another entity.
What is foreign key? A relation schema r1 derived from an ER schema may contain among its attributes the primary key of another relation schema r2.this attribute is known as a
What will be create when a primary key if combined with a foreign key? A primary key if combined with a foreign key it creates Parent-Child relationship between the tables that
What are the two methods for dealing deadlock problem? The two procedures for dealing deadlock problem is deadlock detection and deadlock recovery.
why three level architecture had been developed/
Describe an data dictionary? A data dictionary is a data structure which keeps meta data about the structure of the database ie. the schema of the database.
Write the motivations led to development of OO-DBMS? 1. Programmer frustration with RDBMSs. 2. Requirement for special features.
Explain Record Based Logical Models? Record-Based logical Models: Also define data at the conceptual and view levels. Unlike object-oriented models, are used to state overall
UNION If R1 and R2 are two union compatible relations then R3 = R1 ∪ R2 is the relation having tuples that are either in R1 or in R2 or in both. In case, R3 will have tuples
What is a data dictionary? Data Dictionary is a main source of data in a data management system. Its major function is to carry the creation and management of data definition
What is the archtetype/instance pattern? The archetype/instance pattern happens when one entity tracks occurrences of another entity. A common example is the relationship among
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