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What do you mean through integrity constraints?
Integrity Constraints -An integrity constraint is a condition specified on a database schema and restricts the data in which can be stored within an instance of the database. If a database instance satisfies all the integrity constraints described on the database schema, it is a legal instance. A DBMS enforces integrity constraints, in which it allows only legal instances to be stored in the database.
Describe Parameteric end users? Parametric end users might be given update access, but are commonly not permitted to change the structure of data.
Explain three main attributes of data.
Rules Of Data Normalisation Let us now summarise Normalisation with the help of various clean rules. The following are the necessary rules for the Normalisation process: 1.
Mappings between Levels and Data Independence The 3 levels of abstraction in the database do not exist separately of each other. There must be some correspondence, or mapping
What are the uses of functional dependencies? To test relations to see whether they are legal under a given set of functional dependencies. To state constraints on the set
It defines that the tuple in one relation that refers to another relation must refer to an existing tuple in that relation. This constraint is states on two relations (not essentia
What is the use of group by clause? Group by clause is used to apply aggregate functions to a set of tuples. The attributes given in the group by clause are used to
What is difference between primary index and secondary index? Primary Index a) It is an ordered file whose records are of fixed length along with two fields. b) Only base
What is the way a particular application views the data from the database that the application uses? Sub schema is the way a particular application views the data from the data
For each 1: n relationship type R involving two entities E1 and E2, we recognize the entity type (say E1) at the n-side of the relationship type R and contain primary key of the en
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