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What are the types of reference?explain it with suitable examples?
Object oriented language given the ability to refer the object attribute of the type can be referred to the specified type. We can describe the type dept with a field name and a field head which is reference to the type person and a table dept of the type dept as followed
Create type dept(
Name varchar(20),
Head ref(person)scope people
)
Create table dept of dept
The table definition must state that the reverence is derived and must still state a self referential attribute name. When interesting a tuple for dept we can then use
Insert into dept
Values('CS','john')
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What is the difference between WHERE and HAVING clauses?. Predicates in the WHERE clause applies to every tuple while the predicate in the HAVING clause applies to groups.
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Given the following relations Vehicle (Reg_no, make, colour) Person(eno, name, address) Owner(eno, reg_no) Write expressions in the relational algebra to answer the following
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Example -Find the employee name, salary, department number and average salary of his/her department, for those employees whose salary is more than the average salary of that depart
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What is disadvantage of multiple inheritances? There is potential ambiguity if the similar variable or method can be inherited from more than one superclass.eg: student class m
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