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Define cardinality and participation constraints on a relationship type, completeness constraint on generalization.
Ans: Cardinality defines the number of entities to which other entity can be related via a relationship set. It may be 1:1, 1: N or M: N.
In a relationship set Participation of an entity set can be total or partial. It is total if each entity participates in the relationship. If only a few entities participate in a relationship after that it is partial.
Completeness constraint may be partial or total. In the case of total every higher level entity must belong to a lower level entity and in the case of partial few higher level entities might not belong to lower level entities.
Entity types that do not have any key attribute, and therefore cannot be identified independently, are known as weak entity types. A weak entity can be recognized uniquely only by
Key to represent relationship amongs tables is called ? A Key that represent the relationship between tables is called Foreign Key.
Define the Third Normal Form: The third normal form (3NF) is a normal form employed in database normalization. 3NF was initially defined by E.F. Codd in 1971. Codd's definitio
Explain Data Sublangauges ? Data sublanguage: In relational database theory, the term sublanguage, first used for this purpose through E. F. Codd in the year of 1970, refers t
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Strong entity set and weak entity set? Strong entity set and weak entity set: A strong entity set has a primary key. All tuples in the set are distinguishable through that key.
Illustrate the statement 'Projection operation distributes over the union operation'. Give an example. Ans: Π L (E 1 ∪ E 2 ) = (Π L (E 1 )) ∪ (Π L (E 2 )) This says th
What subschema expresses ? A subschema expresses the external view. (External schemas are called also called as subschemas)
A Structure of a dependency diagram
Explain recovery process after system failure using checkpoint. Ans: Checkpoint scheme or method is an extra component of the log based recovery system. This scheme is used to
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