We use the SQL construct COUNT(*) to count the number of rows in a table.
Answer: A
Correct answer: True
COUNT(*) counts the rows in a table or in each group of a grouped query, including rows containing nulls. It is the first thing to run on an acquired table, since the row count establishes the scale of what you are dealing with before any structural inference is attempted.
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The design guidelines and priorities for read-only databases are different because read-only databases are never updated.
Answer: A
Correct answer: True
Because a read-only database is never updated, modification anomalies cannot occur, and the chief reason for normalizing disappears. What remains is the cost of joins, so the priorities invert: denormalized structures that answer queries in fewer joins are preferred, and the design is judged on retrieval performance rather than on update integrity.
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When assessing the table structure of an acquired set of tables with data, accessing the validity of possible referential integrity constraints on foreign keys is (part of) the:
Answer: C
Correct answer: third step.
The assessment proceeds in order: first count the rows and examine the columns to see what is there, then determine the functional dependencies, primary keys and foreign keys, then assess whether the referential integrity constraints those foreign keys imply are actually satisfied by the data. The check comes third because it cannot be made until the foreign keys have been identified.
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Most of the time, modification anomalies are serious enough that tables should be normalized into:
Answer: D
Correct answer: BCNF.
Boyce-Codd Normal Form requires every determinant to be a candidate key, and a table satisfying it is free of the anomalies that arise from functional dependencies. Third normal form leaves some cases unhandled, which is why BCNF rather than 3NF is the practical target. Beyond it, 4NF deals with multivalued dependencies, which are a separate matter.
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When building a database from an existing set of tables, we still need to consider normalization principles.
Answer: A
Correct answer: True
The tables you are given were designed by someone else, often for a different purpose, and may carry every problem normalization exists to prevent. Understanding their dependencies and deciding what to normalize is part of building a sound database from them - and even where you choose to leave a table denormalized, that should be a decision rather than an oversight.
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Needing to assess the validity of assumed referential integrity constraints on foreign keys is a(n) ________ of normalization.
Answer: D
Correct answer: disadvantage
Normalization decomposes one relation into several linked by foreign keys, and every foreign key brings a referential integrity constraint that must be assessed and then enforced. That work would not exist without the decomposition, so it counts as a cost of normalizing - the second of the two standard disadvantages, alongside the more complicated SQL that the extra tables require.
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In all cases, normalization into BCNF is desirable.
Answer: B
Correct answer: False
Normalization removes modification anomalies at the cost of more tables, more joins and more complex SQL, and where anomalies cannot arise the cost buys nothing. A read-only database is the standard case, and reporting and warehouse designs are deliberately denormalized. BCNF is the usual target for an updateable database, not a universal rule.
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Multivalued dependencies create harmless anomalies that should be noted, but do not always need to be eliminated.
Answer: B
Correct answer: False
Multivalued dependency anomalies are not harmless. Two independent multivalued facts in one relation force every combination of them to be stored, so adding one value of the first requires a new row for every existing value of the second, and the redundancy grows as their product. Splitting the relation removes the problem entirely.
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Each answer below shows example data from a table. Which answer is an example of the missing values problem?
Answer: C
Correct answer: Three rows have the values Brown, NULL, and Blue in the same column.
The missing values problem is the presence of nulls, and the difficulty is that a null is ambiguous: it may mean the value is unknown, or that it does not apply, or that nobody has entered it yet. Since the three call for different treatment and the data does not distinguish them, every null has to be investigated rather than assumed.
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We have normalized a table into BCNF if all candidate keys are determinants.
Answer: B
Correct answer: False
The condition runs the other way: BCNF requires every determinant to be a candidate key. Candidate keys are always determinants in any relation, since identifying a row fixes all its attributes, so the statement as written is true of every relation and tests nothing. The requirement that bites is that no determinant may be anything other than a candidate key.
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