______contains information that defines valid values that are stored in a column or data type.
Answer: B
Correct answer: Rule
A rule is bound to a column or a user-defined data type and specifies which values are acceptable there. A default supplies a value when none is given, and an index affects only how rows are found.
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A ____ key specifies a uniqueness constraint that no two distinct tuples in any state r of relation R can have the same value for super key.
Answer: D
Correct answer: Super
A super key is any set of attributes whose values are unique across the relation. A candidate key is a super key with no redundant attribute in it, so every candidate key is a super key but not the reverse.
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The drawback of shadow paging technique are
Answer: D
Correct answer: All of these
Shadow paging avoids undo and redo but pays for it in three ways: committing means switching page tables and flushing, related pages become scattered because updates are written elsewhere, and the superseded pages have to be reclaimed afterwards.
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Isolation of the transactions is ensured by
Answer: C
Correct answer: Concurrency control
Isolation - that each transaction behaves as though it ran alone - is what the concurrency control component provides, through locking or timestamping. Atomicity and durability are the transaction and recovery managers' business.
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HSAM stands for .
Answer: B
Correct answer: Hierarchic Sequential Access Method
HSAM is Hierarchic Sequential Access Method, one of the IMS access methods, in which the segments of a hierarchical database are stored in sequential order.
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The ______ operator is used to compare a value to a list of literal values that have been specified.
Answer: A
Correct answer: IN
IN tests whether a value appears in a list, as in \( \text{city IN ('Delhi','Mumbai','Pune')} \). LIKE matches a pattern against a single string and BETWEEN tests a range.
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An advantage of the database management approach is
Answer: C
Correct answer: data is integrated and can be accessed by multiple programs
The point of the database approach is that data is held once, in one place, and shared: many programs read the same integrated store instead of each keeping its own file. Redundancy falls rather than rises, and the data becomes independent of the programs.
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In an ER diagram the ___shape specifies the Attibute and a ____ shape specifies the primary key attribute.
Answer: A
Correct answer: Oval; An oval with an underlined attribute
In an E-R diagram an attribute is drawn as an oval, and the attribute that serves as the primary key is shown by underlining its name. Rectangles are entities and diamonds relationships.
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Change Staff table by removing default of Assistant for position column
Answer: A
Correct answer: ALTER TABLE Staff ALTER position DROP DEFAULT;
Removing a default is a change to the column, so the statement is ALTER TABLE, then ALTER on the named column, then DROP DEFAULT. Omitting the column name leaves the clause with nothing to act on, and MODIFY is not the keyword that begins the statement.
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The _____ category includes storage media that can be operated on directly by the computers central processing unit.
Answer: A
Correct answer: Primary storage
Primary storage - main memory and cache - is the storage the CPU can address directly. Secondary storage such as disk must be read into primary storage before the processor can work on it.
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