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I have a question according to the relational model database
Posted on 2011-03-23
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
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
[X]
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5 Comments
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...
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...
Active today
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."
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."
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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