Read-only databases are ________ updated.
Answer: D
Correct answer: never
A read-only database is by definition never updated after it is loaded, which is what changes its design priorities: modification anomalies cannot occur, so normalization loses its purpose and denormalized structures may be preferred for query speed. Data is refreshed by reloading rather than by updating in place.
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If a table has been normalized so that all determinants are candidate keys, then that table is in:
Answer: D
Correct answer: BCNF.
This is the definition of Boyce-Codd Normal Form: every determinant - every left-hand side of a functional dependency - must be a candidate key. A determinant that is not a key allows the same fact to be repeated across many rows, which is precisely what produces update anomalies. Note the direction: all determinants must be candidate keys, not the reverse.
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When assessing the table structure of an acquired set of tables with data, determining primary keys is (part of) the:
Answer: B
Correct answer: second step.
Determining the primary keys belongs to the second step, along with the functional dependencies from which they follow and the foreign keys that depend on them. The row and column survey comes first, and testing whether the referential integrity constraints implied by those foreign keys actually hold comes third.
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Each answer below shows example data from a table. Which answer is an example of the general-purpose remarks column problem?
Answer: D
Correct answer: One row has the value "He is interested in a Silver Porsche from the years 1978-1988" in a column.
A general-purpose remarks column holds free text into which users put whatever they think worth recording, so the same column contains different kinds of fact in different rows. It cannot be queried reliably, cannot be validated, and the information in it - here a colour, a model and a year range - belongs in columns of its own.
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Any table that meets the definition of a relation is said to be in first normal form.
Answer: A
Correct answer: True
First normal form is simply the definition of a relation restated: single-valued cells, homogeneous columns, no duplicate rows, no significance to order. So any table that qualifies as a relation is already in 1NF, and getting into it is a matter of eliminating repeating groups and multivalued cells rather than of examining dependencies.
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Using the SQL GROUP BY phrase with a SELECT statement can help detect which of the following problems?
Answer: B
Correct answer: The inconsistent values problem
Grouping on a column and counting the members of each group exposes values that should be the same but are not: variant spellings, different word orders and stray punctuation each form their own group. A quick look at the group list makes the inconsistency obvious in a way that scanning the rows would not.
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When assessing the table structure of an acquired set of tables with data, counting the number of table rows is (part of) the:
Answer: A
Correct answer: first step.
Counting the rows and examining what columns exist is the first step, because it establishes the scale and the shape of what has arrived before any inference is attempted. Only then can functional dependencies and keys be worked out in the second step and the referential integrity constraints tested in the third.
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Denormalized tables are in BCNF.
Answer: B
Correct answer: False
Denormalized is precisely the opposite of BCNF: the tables have been recombined, or left combined, so that determinants which are not candidate keys remain. That is done deliberately to avoid joins, and it is a reasonable choice for read-only data, but it means accepting the duplication and the anomalies that BCNF would have removed.
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We can eliminate modification anomalies with proper normalization that results in tables in BCNF.
Answer: A
Correct answer: True
Anomalies arising from functional dependencies come from determinants that are not candidate keys, and BCNF is defined precisely by the absence of those. Removing them removes the anomalies. Multivalued dependencies are a separate source and need fourth normal form, but for the functional case BCNF is sufficient.
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Creating a read-only database is a task that is ________ assigned to beginning database professionals.
Answer: B
Correct answer: commonly
Building a read-only database from a set of extracted tables is a well-defined, low-risk task with no update logic to get wrong, which is why it is a common first assignment. The design priorities are different too: since nothing will be updated, modification anomalies cannot arise and the tables are often deliberately left denormalized for speed.
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