DBMS is a collection of _____ that enables user to create and maintain a database.
Answer: B
Correct answer: Whenever a 1 is present at an input
NOR is the complement of OR. OR is 1 as soon as any input is 1, so NOR is 0 in that case, and it is 1 only when every input is 0.
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Immediate database modification technique uses
Answer: A
Correct answer: Both undo and redo
With immediate modification a transaction's writes reach the database before it commits, so an uncommitted transaction's changes must be undone after a crash, and a committed transaction's changes that had not yet reached disk must be redone. Deferred modification needs redo only, since nothing is written before commit.
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The clause alter table in SQL can be used to
Answer: D
Correct answer: all of the above
ALTER TABLE covers every change to a table's definition: adding a column, dropping one, and changing a column's type, default or constraints.
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Processed data is called _____
Answer: C
Correct answer: Information
Data are raw facts; once they have been organised, summarised or interpreted so that they mean something, they are information. That is the distinction on which the whole subject rests.
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Assume transaction A holds a shared lock R. If transaction B also requests for a shared lock on R.
Answer: C
Correct answer: It will immediately be granted.
Shared locks are compatible with one another, since reading does not interfere with reading. B would have to wait only if A held an exclusive lock or if B were asking for one.
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Create a table with the following attributes: Employee(EMPNO integer, EMPNAME of 10 characters)
Answer: A
Correct answer: Create table Employee(EMPNO int, EMPNAME char(10));
A ten-character column is declared char(10); String is not an SQL type and a bare string has no length. The table must also be named as the question specifies, which rules out the options calling it Emplo or Emp.
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In a relational schema, each tuple is divided into fields called
Answer: A
Correct answer: Domains
A relation is defined over a set of attributes, each drawn from a domain - the set of permitted values for that field. So the fields into which a tuple divides correspond to the domains of the relation. Relations are the tables themselves, one level up.
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Data independence means
Answer: D
Correct answer: both B and C
Data independence has two halves: physical independence means programs do not depend on how the data is stored, and logical independence means they survive changes to the logical structure. Both are meant by the term, which is why the two options are taken together.
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Which of the following is not a consequence of non-normalized database?
Answer: D
Correct answer: Lost update problem
Update anomalies, insertion anomalies and redundancy are all consequences of a badly normalised design and would appear with a single user. The lost update problem arises from two transactions running at the same time, which is a concurrency issue.
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According to the levels of abstraction, the schema at the intermediate level is called
Answer: D
Correct answer: Logical schema.
The three levels of abstraction are physical at the bottom, logical in the middle and external, or view, at the top. The logical schema describes the whole database as tables and relationships without saying how it is stored.
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