targate 10 -Id 2260

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targate 10 -Id 2260

Postby amitmandal03 » Sun Jan 20, 2013 3:25 pm

q no 21 :
don't you think first statement is false ???
correct sequence should be FFT (no option given )

i am saying this based on question no 18 -targate-8-Id 2259
gateforum explained answer of count as 3 :( they didn't take null values. then why are they considering here ?

share ur views !
~Amit
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Re: targate 10 -Id 2260

Postby MonikaD » Sun Jan 20, 2013 5:53 pm

I think it should be TFT. null is taken in to accou
for count operation
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Re: targate 10 -Id 2260

Postby amitmandal03 » Sun Jan 20, 2013 5:58 pm

then what abt TarGATE 8 q.no -18???
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Re: targate 10 -Id 2260

Postby zealdeal » Sun Jan 20, 2013 6:52 pm

Answer is FFF. And the answer key also says that. 3rd statement cant be true, because select clause may return duplicate tuples while project operation cant.

Using "select distinct" clause in SQL will make it similar to project operation in relational algebra.
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Re: targate 10 -Id 2260

Postby HimaMehta » Sun Jan 20, 2013 7:15 pm

amitmandal03 wrote:q no 21 :
don't you think first statement is false ???
correct sequence should be FFT (no option given )

i am saying this based on question no 18 -targate-8-Id 2259
gateforum explained answer of count as 3 :( they didn't take null values. then why are they considering here ?

share ur views !

I do agree with you .... and even korth says that.. projection is same as selection !!!
God is REAL, unless explicitly declared INTEGER.!!!
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Re: targate 10 -Id 2260

Postby amar2013 » Sun Jan 20, 2013 8:33 pm

zealdeal wrote:Answer is FFF. And the answer key also says that. 3rd statement cant be true, because select clause may return duplicate tuples while project operation cant.

Using "select distinct" clause in SQL will make it similar to project operation in relational algebra.

I agree with this.In projection duplicate tuples are removed where in select can return duplicate tuples.
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Re: targate 10 -Id 2260

Postby amitmandal03 » Mon Jan 21, 2013 7:57 am

zealdeal wrote:Answer is FFF. And the answer key also says that. 3rd statement cant be true, because select clause may return duplicate tuples while project operation cant.

Using "select distinct" clause in SQL will make it similar to project operation in relational algebra.

oops ! i was fighting for null values . thought answer is given as TFT(C) :D
anyway! u are correct.. 3rd statement is false :)
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Re: targate 10 -Id 2260

Postby MonikaD » Mon Jan 21, 2013 9:11 am

Regarding the first sentence :

Except count, all aggregations apply to a single attribute. Here, we are trying to use count on a single attribute.
Second of all , i do not know what TARGATE solutions suggest is ryt or wrong but All aggregate functions except count(*) ignores tuples with null values.I read this statement in silberchatz, (i am looking for the page number)

comments please!!
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Re: targate 10 -Id 2260

Postby amitmandal03 » Mon Jan 21, 2013 10:43 am

MonikaD wrote:Regarding the first sentence :

Except count, all aggregations apply to a single attribute. Here, we are trying to use count on a single attribute.
Second of all , i do not know what TARGATE solutions suggest is ryt or wrong but All aggregate functions except count(*) ignores tuples with null values.I read this statement in silberchatz, (i am looking for the page number)

comments please!!

count can be applied on single attribute !

COUNT(Name) does not count NULL values, but COUNT(*) does!
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Re: targate 10 -Id 2260

Postby nikhilbhr » Mon Jan 21, 2013 10:57 am

HimaMehta wrote:
amitmandal03 wrote:q no 21 :
don't you think first statement is false ???
correct sequence should be FFT (no option given )

i am saying this based on question no 18 -targate-8-Id 2259
gateforum explained answer of count as 3 :( they didn't take null values. then why are they considering here ?

share ur views !

I do agree with you .... and even korth says that.. projection is same as selection !!!

no selection can do projections work but projection cant do selection work
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