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Trắc Nghiệm SQL - Bài 26
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1-
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Nulls, if used improperly, can create problems because they can represent:
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A -
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An unknown attribute value.
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B -
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A known, but missing, attribute value.
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C -
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A "not applicable" condition.
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D -
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All of the above
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2-
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SELECT C1.CustName, C1.SalesRepNo
FROM CUSTOMER C1;
the "C1" is called a(n) ________________ .
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A -
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term
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B -
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alias
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C -
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convention
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D -
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phrase
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3-
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The following table and functional Dependencies exhibits what type of dependency?
Table (A, B, C)
A -> C
A -> B
B -> C
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A -
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Transitive Dependency
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B -
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Full Dependency
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C -
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Partial Dependency
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D -
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A and B
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4-
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A table that meets the requirements of a relation is said to be in which normal form?
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A -
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first normal form
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B -
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second normal form
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C -
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third normal form
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D -
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Boyce-Codd Normal
Form
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5-
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A relation scheme R is in 3rd normal form if
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A -
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Each nonprime attribute in R is fully dependent on every key.
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B -
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R satisfies 2nd normal form and no nonprime attribute of R is transitively dependent of the primary key.
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C -
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R contains only 3 keys
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D -
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All attribute in R have atomic domains.
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6-
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Under what condition(s) is a relation always in 2NF?
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A -
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When all functional dependencies are partial
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B -
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(II) if there is only one, single attribute key
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C -
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(I) and (II)
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D -
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(I) if every candidate key is a single attribute key.
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7-
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Which of the following is not a relation?
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A -
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X(B, C)
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B -
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Y(D, E, F)
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C -
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W(A)
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D -
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Z(J, K(L, M))
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8-
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Consider a relation R with five attribute A B C D E. You are given the following dependencies: A-
>B, B C->E and E D->A. R is:
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A -
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1NF
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B -
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2NF(khóa là ACD,BCD,ECD)
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C -
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3NF
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D -
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BCNF.
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9-
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Table TT {A, B, C, D, E} and a set of functional dependencies A->D,E ; D->B,C; A,C->B; The
primary key is
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A -
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AE
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B -
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A
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C -
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DA
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D -
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AB
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10-
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Table TT{A, B, C, D, G, H} and a set of functional dependencies G,H->A,D; A,G->B ; C,D->G,H;
C->A; B,H->C;
The closure of {A B H} is:
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A -
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A B C D G
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B -
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A C G H
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C -
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A B C H
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D -
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A C G H B
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[Người đăng: Thành Lãm - ST] |
