What are characteristics of projections in Vertica? (Select three.)
A.
A projection can contain data from one or more source tables.
B.
A projection can contain data from only one source table.
C.
A projection can contain a subset of rows from the source table.
D.
Each projection contains all rows from the source table.
E.
A projection can contain a subset of columns from the source table.
F.
Each projection contains all columns from the source table.
Explanation:
http://184.106.12.19/2011/09/02/the-power-of-projections-part-2/
The answer is : A ,B ,E
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A and B exclude each other. Is it a typo ?
My choice is: A (pre-join projections), D and E.
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Oh Alexey ,
sorry my bad. Also selection D is true. You’re exactly right.
But also selection B is true. Because you can manually create projection related to only one source table like
“Create projection test_projection as select * from test_table”.
As you can see , test_projection is related to only one source table(test_table).
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Hmm, it is kind of philosophic 🙂
A: …..from ONE or MORE……
B: ……from ONLY ONE……..
I read B as ONLY ONE and NOT MORE THAN ONE.
And A already covers that case you mentioned:
“Create projection test_projection as select * from test_table”.
So, I am still believe B is not correct. At least if we can choose just 3 of 6 I will not select B
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If there is a question like Can projection contain data from only one source table ?
What would be your answer ? Yes or no ? If you do not select B , your answer would be no.
Then I have a question. Can you explain what superprojection is ? Does superprojection contaion data from more than one table ? 🙂
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Alexey ,
forget my last entry.It is a philosophical question 🙂
Now I agree with you 😛 😛
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sorry answers are wrong i agree with Zubir A,C,E request u to relook the answers
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Alexey, firat –
Have you considered segmented projections? In case of a segmented projection D would be wrong and C correct, or am I wrong?
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if it is a aggregated projection , top k or live aggregate projection not all rows in source table are necessary.
A C E are correct
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