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Write a short note on built in function in QBE?
Built in function in QBE: QBE involves various built in functions like AVG, MAX,MIN,SUM and CNT. We must prefix these operators along with ALL to create a multiset on that the aggregate operation is evaluated. The ALL operator ensures in which duplicates are not eliminated. We can use UNQ to specify which we want duplicates eliminated. QBE also offers the ability to calculate functions on groups of tuples by using the G operator, that is analogous to SQL's group by construct.
Find the names of all Albums that have more than 30 tracks. Result: (name: varchar(255))
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
Primary Key The primary key is the candidate key that is selected by the database designer as the principal denotes of identifying entities within an entity set. The left candi
What is meant by functional dependencies? Consider a relation schema R and α C R and β C R. The functional dependency α ->β holds on relational schema R if in any legal relati
(a) Why did SAP introduce the extended star schema?
In a relation, tuples are not inserted in any definite order. Ordering of tuples is not defined as a part of a relation definition. Though, records may be structured later accordin
The advantages of a database management system (DBMS) include :- Data integrity and elimination of duplication.
Data Replication "If a relation R has its copies kept at two or more sites, then it is considered replicated". But why do we replicate a relation? There are several advan
MOSS VALE is a town with 15000 inhabitants. The fire department wishes to develop a system that automates the despatch of fire engines to attend fires. The ERD below describes the
What is System R? What are its two major subsystems? System R was intended and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its pur
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