A field represents each component of a composite attribute.
Answer: A
Correct answer: True
A composite attribute is stored as one field per component - street, town and postcode rather than a single address field - whenever the parts will be used separately. Storing it whole is the alternative, and the choice turns on whether anything will ever need to search or sort on a part.
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Which of the following are integrity controls that a DBMS may support?
Answer: D
Correct answer: All of the above.
All three are integrity controls the DBMS itself can enforce: a default supplied when no value is given, a domain constraint limiting the permissible values, and a not-null constraint requiring one. Placing them in the database rather than in each application means every route to the data is checked identically.
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The three newest database architectures in use today are relational, multidimensional and hierarchical.
Answer: B
Correct answer: False
The hierarchical model is the oldest of the architectures, dating from the 1960s. The three newest in general use are relational, object-oriented and multidimensional. Including hierarchical among the newest inverts the chronology of the whole subject.
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A multidimensional database model is used most often in which of the following models?
Answer: A
Correct answer: Data warehouse
The multidimensional model organises data as measures indexed by dimensions - sales by product by region by month - which is exactly how analytical questions are asked. It suits the warehouse for that reason, and suits transaction processing badly, since it is designed to be read rather than updated.
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It is usually not very important to design the physical database to minimize the time required by users to interact with the information systems.
Answer: B
Correct answer: False
Response time as the user experiences it is very nearly the point of physical design. The logical design is already correct; what physical design adds is the indexing, organisation and placement that decide whether the system is usable, and user interaction time is the measure that matters most.
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Which of the following improves a query's processing time?
Answer: D
Correct answer: Use compatible data types.
Comparing columns of different types forces the database to convert one of them, and a converted column generally cannot use its index - so a query that should have been an index lookup becomes a full scan. The other three options all add work: complexity, self-joins and subqueries each give the optimiser more to do rather than less.
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A bitmap index is an index on columns from two or more tables that come from the same domain of values
Answer: B
Correct answer: False
An index on columns from two or more tables drawn from the same domain is a join index, which exists to avoid computing the join at query time. A bitmap index is something else: one bit vector per distinct value, which is compact and fast where a column has few distinct values.
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Which of the following is an advantage of partitioning?
Answer: D
Correct answer: Security
Partitioning lets the sensitive rows or columns be placed in their own partition with its own access controls, so a user reaching one part of a table need not be given the whole of it. The other three options are the recognised disadvantages - more complexity, uneven access speed, and extra space for the partitioning structures.
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In general, larger block sizes are used for online transaction processing applications and smaller block sizes are used for databases with a decision support or data warehousing system.
Answer: B
Correct answer: False
The sizes are the other way round. Transaction processing touches few rows at a time and benefits from small blocks, which reduce contention and wasted transfer. Warehousing scans large ranges, so large blocks bring more useful data per read. The statement has the two applications exchanged.
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Selecting a data type involves which of the following?
Answer: C
Correct answer: Improve data integrity
Choosing a type that admits only the values the attribute can legitimately take is itself a constraint: a date column will not accept a non-date, and a numeric one will not accept text. The other options are the reverse of what is wanted - storage should be minimised, and a type admitting the widest range of values weakens the check.
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