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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:
Define the basic operations of the relational algebra? Ans: Basic operators of relational algebra are: 1. Union (∪) - Selects tuples which are in either P or Q or in bot
explain various steps uses in evaluation and maintenance of MIS.
What is equi join? Equi Join - It generates all the combinations of tuples from two relations which satisfy a join condition along with only equality comparison (=).
Consider the relations City (city_name, state) Hotel (name, address) City_hotel (hotel_name, city_name, owner) Answer the following queries in relational algebra (i) Find
what is 3nf
WOUND-WAIT
What is Object Oriented model? This model is based on collection of objects. An object has values stored in instance variables with in the object. An object also having bodies
What is Asterisk in SQL? Asterisk (*): In SQL, the columns for all the tables and views in the FROM clause will be displayed.
The Internal or Physical Level The collection of files permanently stored on secondary storage devices is called as the physical database. The internal or physical level is t
Why did SAP introduce the extended star schema? Explain why it is reported to be better than the traditional schema model?
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