A database design may be based on existing data.
Answer: A
Correct answer: True
A design may well start from data that already exists - spreadsheets, legacy files, another system’s tables. The process is different from designing from requirements: the existing structures have to be analysed and normalised rather than derived, and this is where much real database work begins.
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In E-R diagram generalization is represented by
Answer: D
Correct answer: Triangle
Generalisation and its inverse, specialisation, are drawn as a triangle labelled ISA, connecting the general entity set above to the specialised ones below. An ellipse is an attribute, a dashed ellipse a derived one, and a rectangle an entity set.
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The following are functions of a DBMS except ________ .
Answer: A
Correct answer: creating and processing forms
A DBMS creates databases, processes data and provides the tools to administer them - backup, security, concurrency. Forms belong to the application, not to the DBMS: they are the user interface built on top of it. (Products such as Access blur the line by bundling both, which is what makes this question worth asking.)
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Cross Product is a:
Answer: C
Correct answer: Binary Operator
The Cartesian product takes two relations and returns one, so it is a binary operator - as are union, difference, intersection and join. Selection and projection are unary, taking a single relation.
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In __________ data can be stored in structured manner.
Answer: C
Correct answer: Database
A database stores data in a structured way: organised into tables of typed columns, with keys and defined relationships between them. The CPU and ALU are processing hardware and store nothing of the kind.
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What is a relationship called when it is maintained between two entities?
Answer: B
Correct answer: Binary
A relationship’s degree is the number of entity types it connects: binary for two, unary (recursive) for one entity type related to itself, ternary for three. Binary relationships are much the most common.
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Database applications are seldom intended for use by a single user.
Answer: B
Correct answer: False
Plenty of database applications are meant for a single user - a personal contact list, a small stock record, most Access databases. The multi-user case is the harder and more interesting one, but it is not the only one.
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Consider the join of a relation R with relation S. If R has m tuples and S has n tuples, then the maximum size of join is:
Answer: A
Correct answer: mn
A join is a selection applied to the Cartesian product, so it can never return more tuples than the product itself, which has \(m \times n\). That maximum is reached only when the join condition matches every pair - in effect a cross join. A typical equijoin on a foreign key returns far fewer.
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Which of the following is another name for weak entity?
Answer: A
Correct answer: Child
A weak entity has no key of its own and depends on an owner for its identity, so it is also called the child or subordinate entity; the entity it depends on is the owner, parent or dominant one. A loan payment identified only by its number within a given loan is the classic example.
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The database environment has all of the following components except:
Answer: B
Correct answer: Separate files
The database environment consists of users, applications, the DBMS, the database and the database administrator. Separate files are precisely what it replaces - the pre-database arrangement, in which each application kept its own file and the same data was duplicated and grew inconsistent.
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