In a relation, the columns are sometimes called "attributes."
Answer: A
Correct answer: True
Columns are attributes in the relational vocabulary, fields in the older file-processing one. Each attribute draws its values from a single domain, and attributes are identified by name rather than by position, which is why the order in which the columns are written does not matter.
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Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:
Answer: A
Correct answer: A → B.
A functional dependency holds when each value of the determinant is always paired with one and the same value of the dependent attribute. Here A always brings the same B, so A determines B; but A appears with different values of C, so A does not determine C, and it cannot determine the pair (B, C) either. The last option reverses the direction, for which the data give no evidence.
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A relation is in 5NF when multivalued dependencies are isolated in their own relation.
Answer: B
Correct answer: False
Isolating multivalued dependencies in their own relations gives fourth normal form, not fifth. Fifth normal form, sometimes called project-join normal form, deals with join dependencies: relations that cannot be reconstructed correctly from any two of their projections but can from three or more.
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A key:
Answer: C
Correct answer: identifies a row.
A key identifies rows, not columns, and it may consist of one attribute or several - a key of two or more is a composite key, but there is no requirement either way. What matters is that the combination be unique across the relation and minimal, so that no attribute could be dropped and uniqueness still hold.
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A relation is considered a:
Answer: C
Correct answer: two-dimensional table.
A relation is a two-dimensional structure of rows and columns in which each cell holds a single value, all entries in a column are of one kind, no two rows are identical, and neither the row order nor the column order carries meaning. Those conditions together are what distinguish a relation from a table in the loose sense.
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A functional dependency is a relationship between or among:
Answer: D
Correct answer: attributes.
A functional dependency is a statement about attributes within a relation: given a value of the determining attribute, the value of the dependent one is fixed. It is a property of the meaning of the data rather than of the rows that happen to be stored, so it cannot be established by inspecting a sample - only refuted by one.
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Normalization reduces data redundancy but generally increases the number of joins needed to answer a query.
Answer: A
Correct answer: True
Splitting data across more, narrower relations removes duplication and the update anomalies that come with it, but reassembling the information then requires joins. This trade-off is why analytical systems often denormalise deliberately.
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A functional dependency is always an equation.
Answer: B
Correct answer: False
A functional dependency is a constraint, not an equation: R → S asserts that each value of R is associated with exactly one value of S, with no arithmetic implied. The values may be names, dates or codes with no numerical relationship at all. The arrow is a statement about determination, not about calculation.
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The only reason for the existence of relations is to store instances of functional dependencies.
Answer: A
Correct answer: True
A relation exists to record which values go with which, and every such association is a functional dependency - the key determines the non-key attributes. Seen that way, storing instances of functional dependencies is what a relation does, and a relation that stores dependencies belonging to more than one theme is exactly the one that suffers modification anomalies.
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A functional dependency is a relationship between or among attributes.
Answer: A
Correct answer: True
A functional dependency relates attributes within a relation: given a value of the determinant, the value of the dependent attribute is fixed. It is not a relationship between tables - that is what a foreign key expresses - nor between rows. Functional dependencies are the language in which every normal form is defined.
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