A table joined with itself is called
Answer: B
Correct answer: Self Join
A self join joins a table to itself, using two different aliases so that the two copies can be distinguished. It is how a table that refers to its own rows is unravelled - listing each employee beside their manager, where both are rows of the same employee table.
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Which of the following products was an early implementation of the relational model developed by E.F. Codd of IBM?
Answer: B
Correct answer: DB2
DB2 was IBM’s commercial relational product, descended from the System R research prototype built to test E. F. Codd’s 1970 relational model. IDMS implemented the older CODASYL network model, and dBase-II and R:base were PC products of the 1980s.
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A data dictionary is a special file that contains:
Answer: D
Correct answer: All of the above
A data dictionary holds the complete description of the data: the name, type and width of every field in every file, together with keys, indexes, constraints and often who may access what. It is metadata, and in a relational database it is itself queryable.
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Which database level is closest to the users?
Answer: A
Correct answer: External
The three-level architecture runs external → conceptual → internal. The external level is closest to the user: each user group sees its own view of the data. The conceptual level is the whole database as one community picture, and the internal level describes how it is physically stored.
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Which one of the following is not true for a view:
Answer: C
Correct answer: View never contains derived columns.
That statement is false: a view may perfectly well define computed columns, such as price * quantity AS total, and doing so is one of its common uses. The other three are true - a view is derived from other tables, it is virtual in the sense that it stores no rows, and its definition is stored permanently in the system catalogue.
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The DBMS ranked as being the "easiest to use" in the text is Oracle Corporation's Oracle.
Answer: B
Correct answer: False
Oracle is ranked the hardest to use, not the easiest - the price of being the most capable and most configurable. Microsoft Access is the easiest of the products discussed, and correspondingly the most limited.
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What are the properties of entities called?
Answer: C
Correct answer: Attributes
The properties of an entity are its attributes - a student’s roll number, name and date of birth. In the implemented database they become the columns of a table.
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Structured Query Language (SQL) is an internationally recognized standard language that is understood by all commercial database management system products.
Answer: A
Correct answer: True
SQL is an international standard, maintained by ANSI and ISO, and every commercial relational DBMS implements it. The qualification worth knowing is that each product adds extensions and differs in the corners, so a complex query is not always portable unmodified - but the core language is common ground.
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In an E-R diagram a relationship type is represented by
Answer: D
Correct answer: Diamond
In the standard E-R notation, a diamond is a relationship type, a rectangle an entity set, and an ellipse an attribute. A double diamond marks the identifying relationship of a weak entity.
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The DBMS that is most difficult to use is ________ .
Answer: D
Correct answer: Oracle Corporation's Oracle
Oracle is the hardest of the four to use, and for a reason: it is the most configurable and the most capable at scale, so it exposes far more to be administered - tablespaces, instances, tuning parameters. Access sits at the other end, easy to use and correspondingly limited.
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