Which of the following is not considered to be a basic element of an enterprise-class database system?
Answer: D
Correct answer: COBOL programs
The basic elements are users, database applications, the DBMS and the database. A COBOL program is merely one possible way of writing an application - a language choice, not an element of the architecture.
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_______ produces the relation that has attributes of R1 and R2
Answer: A
Correct answer: Cartesian product
The Cartesian product \(R_1 \times R_2\) pairs every tuple of one relation with every tuple of the other, so the result has all the attributes of both and \(m \times n\) tuples. Difference and intersection require the two relations to be union-compatible and produce no new attributes at all.
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SET concept is used in :
Answer: A
Correct answer: Network Model
The set is the central construct of the CODASYL network model: a named one-to-many relationship between an owner record type and a member record type, navigated by following pointers. The relational model replaced it with matching key values, and the hierarchical model used parent-child trees.
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The relational model feature is that there
Answer: B
Correct answer: Is much more data independence than some other database models
The relational model’s advantage is data independence: relationships are expressed by matching values in key columns, not by stored pointers, so tables can be reorganised or indexed differently without touching the applications. The older hierarchical and network models embedded the access path in the structure itself, which is what made them rigid.
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The conceptual model is
Answer: D
Correct answer: Independent of both hardware and software
The conceptual model describes what data the organisation needs and how it is related, in terms of the business rather than of any machine or product. That independence is what lets the same model survive a change of hardware or a move to a different DBMS.
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__________________ is collection of interrelated data and set of program to access them.
Answer: C
Correct answer: Database Management System
A DBMS is defined as a collection of interrelated data together with a set of programs to access it. The data alone is the database; adding the software that creates, queries and administers it gives the database management system.
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Which of the following database objects does not physically exist?
Answer: C
Correct answer: View
A view is a stored query: it has no data of its own, and its rows are computed whenever it is referenced. Base tables and indexes both occupy real storage. (A materialised view is the exception that proves the rule - it is stored precisely because an ordinary view is not.)
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A subschema expresses
Answer: C
Correct answer: The external view.
A subschema is the external view: what one particular application or user group sees. The logical view is the whole database as a single community picture, and the physical view is how it is actually stored.
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Which of the following products was the first to implement true relational algebra in a PC DBMS?
Answer: D
Correct answer: R:base
R:base was the first PC product to implement true relational algebra. dBase-II, though far more widely used, was a file-oriented product without genuine relational operations - a distinction that mattered a great deal in the arguments of the mid-1980s.
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A file manipulation command that extracts some of the records from a file is called
Answer: A
Correct answer: SELECT
Select extracts rows that satisfy a condition - the horizontal slice. Project takes columns, join combines two relations on matching values, and product pairs every row with every row. (Confusingly, SQL’s SELECT statement performs projection as well; the relational operator named select is what the WHERE clause does.)
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