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Explain the difference between using functions along with and without grouping attributes in relational algebra. Give examples.
Ans: Group functions are used to group data of similar type. GAMMA = grouping and aggregation Applying GAMMAL(R)• Group R according to all the grouping attributes on list L.1. That is: form one group for each distinct list of values for those attributes in R.• Within each group, compute AGG(A ) for each aggregation on list L.• Result has one tuple for each group:1. The grouping attributes and2. Their group's aggregations. Example: Grouping /Aggregation R = ( A B C ) 1 2 3 4 5 6 1 2 5 GAMMAA,B,AVG(C) (R) = ? First, group R by A and B : A B C 1 2 3 1 2 5 4 5 6 Then, average C within groups: A B AVG(C) 1 2 4 4 5 6
What do you understand by a view? What does WITH CHECK OPTION clause for a view do? - A view is a virtual table which comprises fields from one or more real tables. - It is
Define seek time. The time for repositioning the arm is known as the seek time and it enhances with the distance that the arm is known as the seek time.
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Normalization :It is a process of examine the given relation schemas based on their primary key and Functional Dependencies (FDs) to achieve the properties Minimizing redun
A buyer for a large department store chain must place orders with an athletic shoe manufacturer six months prior to the time the shoes will be sold in the department stores. In par
In E-R Diagram how relationship type is represented ? In E-R Diagram relationship type is represented as a Diamond.
What is Message switching Message switching transmits data units which can be arbitrarily long. Packet switching has a utmost packet size, if any message longer than that, it s
An employee record has the following structure struct employee { int eno; char name[22]; float salary; char dept[10];}; (i) Calculate the record size R in bytes.
Question 1 Explain the concept of Foreign Key. How a foreign key differs from a Primary Key? Can the Foreign Key accept nulls? Question 2 With a necessary example explain (i)
Distributed And Client Server Databases Introduction This unit tells the distributed database systems which are primarily relational and one important execution model: the
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