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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
Define outer union operation of the relational algebra. Compute the outer union for the relations R and S given below. Outer Join - If there are any values in one tabl
Define physical image of a global relation at a site
Problem: A DBMS built for Online Transaction Processing (OLTP) is usually regarded as unsuitable for data warehousing. Each system is designed with a different set of requireme
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Design a generalization–specialization hierarchy for a motor-vehicle sales company. The company sells motorcycles, passenger cars, vans, and buses. Justify your placement of attrib
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