doubts in e-tutor lecture(DBMS and Number System)!!!!!

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doubts in e-tutor lecture(DBMS and Number System)!!!!!

Postby debaleena82 » Mon Apr 18, 2011 1:40 pm

Hi...I have attended the lecture in e-tutor for DBMS Relational algebra.I struct in a doubt for solving a query using relational algebra.
Q1:Given schema for 3 tables:Frequent(Drinker,Pub),Serves(Pub,Beer),Likes(Drinker,Beer)
Write the query using relational algebra:The pub that serves the beer that"Amir" likes..

The query has been solved but it was not clear to me...please resolve and explain it....

Q2:Find out the result of FE base 16 -88 base 16
At the end of the solution I got confused...Please resolve it..

Thanking you,
Debaleena
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Re: doubts in e-tutor lecture(DBMS and Number System)!!!!!

Postby muraligateforum » Mon Apr 18, 2011 2:36 pm

debaleena82 wrote:Hi...I have attended the lecture in e-tutor for DBMS Relational algebra.I struct in a doubt for solving a query using relational algebra.
Q1:Given schema for 3 tables:Frequent(Drinker,Pub),Serves(Pub,Beer),Likes(Drinker,Beer)
Write the query using relational algebra:The pub that serves the beer that"Amir" likes..

The query has been solved but it was not clear to me...please resolve and explain it....

Q2:Find out the result of FE base 16 -88 base 16
At the end of the solution I got confused...Please resolve it..

Thanking you,
Debaleena



(FE) base 16 - (88) base 16 is (76) base 16

FE
88
-----
76
we can justify the solution by converting both of them in to decimal.
that is 254-136 = 118
7x16 + 6 = 118 in decimal.,
muraligateforum
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Re: doubts in e-tutor lecture(DBMS and Number System)!!!!!

Postby debaleena82 » Mon Apr 18, 2011 7:49 pm

Thank you very much professor for getting the reply of one doubt in Number system.

Please help me to resolve the DBMS Query(already mentioned in details in previous post i.e Q1) using Relational Algebra.

Thanking You
Debaleena
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Re: doubts in e-tutor lecture(DBMS and Number System)!!!!!

Postby shekharreddy » Tue Apr 19, 2011 4:49 pm

Hi debaleena82
can see the file for the RA query
pr0000001A.jpg




Natural join of tables ‘Frequent’ and ‘ Likes’ will filter the tuples which are matched on the common column ‘drinker’ and the resultant table will contain the attributes Drinker, Pub, Beer and this table is renamed as ‘D’. From this table we get the information about the beers which are liked by Amir by imposing selection condition “drinker=’Amir’” and projecting only the column ’Beer’ . Now this resultant table is crossed with the table ‘Serves’. Resultant table will contain the columns Pub, Beer, Beer from this we can get the pub names which serve the beers liked by Amir by imposing selection condition ‘Serves.Beer=D.Beer’. As we want only the pub names we will project column ‘Pub’ from the resultant table.
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Re: doubts in e-tutor lecture(DBMS and Number System)!!!!!

Postby debaleena82 » Wed Apr 20, 2011 3:07 am

Thank you very much shekharreddy sir to get the reply in this fantastic manner.I am very much thankful to you.now the query is totally clear to me referring to the attachment.

Thanking you
Debaleena
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