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Explain weak and strong entity type ?
Weak and Strong entity type: An entity set which does not have a primary key is referred to as a weak entity set. The existence of a weak entity set depends on the existence of a strong entity set; it must associate to the strong set via a on-to-many relationship set. A discriminator of a weak entity set is the set of attributes that distinguishes between all the entities of a weak entity set. The primary key of a weak entity set is formed by the primary key of the strong entity set on that the weak entity set is existence depends, plus the weak entity set's discriminator.
A relation instance indicates as r is a collection of tuples for a given relational schema at a exact point of time. A relation state r of the relation schema R (A 1 ,A 2 ,.....
explain external view
Super keys of a relation can have extra attributes. Candidate keys are minimal super key, i.e. such a key have no extraneous attribute. An attribute is known as extraneous if even
Introductory course and so does not require any fancy coding. I will provide a guidance document to help you in producing the solutions.
Increased parallelism : Since the replicated date has several copies a query can be distributed or can be answered from the smallest loaded site. Also, with more replicas you have
Define null values. In some cases a certain entity may not have an applicable value for an attribute or if we do not know the value of an attribute for a certain entity. In the
List out various user authorization to modify the database schema. a) Index authorization b) Resource authorization c) Alteration authorization d) Drop authorizat
In a Hierarchical model of data records are organized ? In the hierarchical model of data records are organized as Tree structure.
For each m:n relationship type R, we make a new table (say S) to represent R. We also contain the primary key attributes of both the participating entity types as a foreign key att
Describe entity referential integrity and integrity. Give an example of each. Entity Integrity Rule - If there is a attribute A of relation R is a prime attribute of R then A
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