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I have a question according to the relational model database

Posted on 2011-03-23
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Last Modified: 2013-11-15
In terms of the relations shown below, what is the appearance of the realtion RESULT after executing each of thesre instructions:
X relation                          Y relation
U V W     RS                                
A Z 5                                3 J
B D 3                                4 K
C Q 5

RESULT <- PROJECT W from X
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Question by:antatiana
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Accepted Solution

by:
BigSchmuh earned 333 total points
ID: 35205287
Projection is an operation to retrieve some of the relation values.
Project W From X should lead you to get the W column as a result.
...and please try to get your homework done by yourself, as you obviously should have this "Projection" information in some reference books...
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LVL 33

Assisted Solution

by:ste5an
ste5an earned 167 total points
ID: 35205466
hi,

BigSchmuh is right. Simply read the basic theory:

http://en.wikipedia.org/wiki/Relational_Database#Relational_operations

"The projection operation extracts only the specified attributes from a tuple or set of tuples."
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Author Comment

by:antatiana
ID: 35232465
thanks. Of course I am doing my homework myself always and this homework was made by ,yself too!!!:) It's just attemp how site is working as I am new here. Of course in all other my quetsions I will follow main rules and if I'd like to ask something from experts according my homework I will do it just in special events if some qeustions are are really very contradictory, I have doubts and I reallyneedhelp of experts to solve my problem.
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LVL 18

Assisted Solution

by:BigSchmuh
BigSchmuh earned 333 total points
ID: 35232932
One must pay the price for asking EEE to spend their time on topics...
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