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Define entity integrity and referential integrity. How does SQL allow specification of these?
Ans: Entity Integrity Rule- If the attribute A of relation R is a prime attribute of R after that A cannot accept null values.
Referential Integrity Rule- In referential integrity, it is made sure that a value that appears in one relation for a given set of attributes as well appears for a particular set of attributes in another relation.
In SQL, referential integrity and entity integrity rules are implemented as constraints on the relation known as reference Key constraint and primary Key constraint correspondingly.
These constraints can be fixed with relation at the time of creation of the relations or after the creation of the relations by altering the definition of the relations. For instance:
Which is a valid SQL type? A valid SQL Should be in CHARACTER it is should be NUMERIC and FLOAT.
Object-based Models: Use objects as key data representation components . Examples:- Entity-Relationship Model: It is a collection of real world objects known as entitie
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i need to implememnt a treee based mining algorithm. do you have an expert that can do that?
Multi-list file Organisation Multi-list file organisation is a multi-index linked file organisation. A linked file organisation is a logical organisation where physical orderin
What are the advantages of creating a table from existing table?
The First Normal Form (1NF) Let us first describe 1NF: Definition: A relation (table) is in 1NF if 1. There are no duplicate tuples or rows in the relation. 2.
What is the use of Union and intersection operation? Union: The result of this operation contains all tuples that are either in r1 or in r2 or in both r1 and r2.Duplicate tuple
In a Hierarchical model of data records are organized ? In the hierarchical model of data records are organized as Tree structure.
Most computer systems authenticate users by asking them for the user name and password. However, the user names and passwords often can be guessed by hackers. Suggest an automated,
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