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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
Give the forms of triggers? The triggering event can be insert or delete. For updated the trigger can state columns. The referencing old row as clause The referencing
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Question: a) Discuss the concept of data independence, explaining its importance in a database environment. b) To address the issue of data independence, the ANSI-SPARC t
Data Fragmentation "Fragmentation includes decomposing the data in relation to non-overlapping component relations". Why do we require fragmenting a relation?
deffine class&object
Given the following set of functional dependencies {cf?bg, g?d, cdg?f, b?de, d?c} defined on R(b,c,d,e,f,g) a.Find a non-redundant cover. b.Find a canonical cover.
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Write short notes on transaction state? A transaction may not always complete its implementation successfully such a transaction is termed aborted A transaction must be in o
State the terms Designing the database and Normalization Designing the database: Out of the ERD we have formed, it is very easy to verify the tables, the attributes which the
Q. What is relational algebra and calculus? Explain the relational algebra operators :- Selection and predicate, set operation, joins and division. Sol. Relational Algebra
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