Database Redesign Questions and Answers

Q: The use of the double NOT EXISTS can be used to find rows that do not match some specified condition.

Correct answer: TrueThe doubly nested NOT EXISTS is the standard SQL expression of relational division: there is no member of the required set for which no matching row exists. It is how one finds, for example, the students who have taken every course in a list, and it is used because SQL has no division operator of its own.

Q: Although creating test databases is a critical and necessary job, there are few career opportunities in this area.

Correct answer: FalseBuilding realistic test databases is a substantial specialism in its own right, requiring data that exercises the boundary conditions, respects the constraints, and is large enough to reveal performance problems - while often being anonymised for privacy. It is a recognised and well-paid area of database work, not a dead end.

Q: Because of the need for extensive knowledge of SQL, many database developers choose to automate the redesign process.

Correct answer: FalseThe extensive SQL knowledge required is a reason for caution rather than for automation. A generated script may be syntactically correct and still lose data or violate a business rule the tool knows nothing about, and against live data such a mistake may be irreversible. Developers therefore use tools to draft changes and then review and test them by hand.

Q: The data model produced from the reverse engineering process does not include intersection table data.

Correct answer: FalseIntersection tables exist physically in the schema, so reverse engineering reads them and includes them like any other table. What it cannot do is recognise that they are intersection tables representing a many-to-many relationship rather than entities in their own right - that interpretation requires a person, and it is one of the reasons the reverse-engineered model needs correction.

Q: If a database is built correctly the first time, it will not have to be redesigned.

Correct answer: FalseNo database stays correct, because the organisation it serves does not stay still. New requirements, new regulations, new products and mergers all change what the data must represent, so redesign follows from changed needs rather than from original error. Building it well the first time makes redesign easier, not unnecessary.

Q: The SQL-92 command to change a table name is RENAME TABLE.

Correct answer: FalseSQL-92 contains no rename command at all. RENAME TABLE is MySQL’s, and the other products each have their own, so a rename cannot be written portably. The standard-conforming route is to create the new table, copy the rows and drop the old one.

Q: Reverse engineering is the process of reading a database schema and producing a data model from that schema.

Correct answer: TrueThat is the definition. Reverse engineering reads an existing schema - tables, columns, keys and constraints - and produces a data model from it, working backwards from the implementation to the design. It is the first step whenever a database must be understood before it can be changed and its documentation is missing or out of date.

Q: The data model produced from the reverse engineering process is a true logical model.

Correct answer: FalseThe model produced is not a true logical model. It reflects the schema as built, including denormalisations, physical compromises and implementation artefacts, and it cannot recover the business meaning that was never recorded in the schema - intersection tables appear as ordinary entities, and optionality and cardinality often cannot be inferred. It is a starting point requiring interpretation, not a finished model.

Q: It is not easy to build a database correctly the first time.

Correct answer: TrueGetting a database right the first time requires knowing the requirements completely and correctly at the outset, which almost never happens, and anticipating changes that have not yet occurred. Requirements are discovered as the system is used, and the organisation changes around it, so some redesign is the normal course of a database’s life rather than evidence of failure.

Q: Typically, exactly two different copies of the database schema are used in the redesign process.

Correct answer: FalseThree copies are used, not two: the operational schema, which is left alone; a test copy on which the changes are proved against representative data; and a copy carrying the proposed new design. With only two, either the testing is done against live data or there is nowhere to develop the new structure.

31.

The use of the double NOT EXISTS can be used to find rows that do not match some specified condition.

A.True
B.False

Answer: A

Correct answer: True

The doubly nested NOT EXISTS is the standard SQL expression of relational division: there is no member of the required set for which no matching row exists. It is how one finds, for example, the students who have taken every course in a list, and it is used because SQL has no division operator of its own.

Discuss in Forum

32.

Although creating test databases is a critical and necessary job, there are few career opportunities in this area.

A.True
B.False

Answer: B

Correct answer: False

Building realistic test databases is a substantial specialism in its own right, requiring data that exercises the boundary conditions, respects the constraints, and is large enough to reveal performance problems - while often being anonymised for privacy. It is a recognised and well-paid area of database work, not a dead end.

Discuss in Forum

33.

Because of the need for extensive knowledge of SQL, many database developers choose to automate the redesign process.

A.True
B.False

Answer: B

Correct answer: False

The extensive SQL knowledge required is a reason for caution rather than for automation. A generated script may be syntactically correct and still lose data or violate a business rule the tool knows nothing about, and against live data such a mistake may be irreversible. Developers therefore use tools to draft changes and then review and test them by hand.

Discuss in Forum

34.

The data model produced from the reverse engineering process does not include intersection table data.

A.True
B.False

Answer: B

Correct answer: False

Intersection tables exist physically in the schema, so reverse engineering reads them and includes them like any other table. What it cannot do is recognise that they are intersection tables representing a many-to-many relationship rather than entities in their own right - that interpretation requires a person, and it is one of the reasons the reverse-engineered model needs correction.

Discuss in Forum

35.

If a database is built correctly the first time, it will not have to be redesigned.

A.True
B.False

Answer: B

Correct answer: False

No database stays correct, because the organisation it serves does not stay still. New requirements, new regulations, new products and mergers all change what the data must represent, so redesign follows from changed needs rather than from original error. Building it well the first time makes redesign easier, not unnecessary.

Discuss in Forum

36.

The SQL-92 command to change a table name is RENAME TABLE.

A.True
B.False

Answer: B

Correct answer: False

SQL-92 contains no rename command at all. RENAME TABLE is MySQL’s, and the other products each have their own, so a rename cannot be written portably. The standard-conforming route is to create the new table, copy the rows and drop the old one.

Discuss in Forum

37.

Reverse engineering is the process of reading a database schema and producing a data model from that schema.

A.True
B.False

Answer: A

Correct answer: True

That is the definition. Reverse engineering reads an existing schema - tables, columns, keys and constraints - and produces a data model from it, working backwards from the implementation to the design. It is the first step whenever a database must be understood before it can be changed and its documentation is missing or out of date.

Discuss in Forum

38.

The data model produced from the reverse engineering process is a true logical model.

A.True
B.False

Answer: B

Correct answer: False

The model produced is not a true logical model. It reflects the schema as built, including denormalisations, physical compromises and implementation artefacts, and it cannot recover the business meaning that was never recorded in the schema - intersection tables appear as ordinary entities, and optionality and cardinality often cannot be inferred. It is a starting point requiring interpretation, not a finished model.

Discuss in Forum

39.

It is not easy to build a database correctly the first time.

A.True
B.False

Answer: A

Correct answer: True

Getting a database right the first time requires knowing the requirements completely and correctly at the outset, which almost never happens, and anticipating changes that have not yet occurred. Requirements are discovered as the system is used, and the organisation changes around it, so some redesign is the normal course of a database’s life rather than evidence of failure.

Discuss in Forum

40.

Typically, exactly two different copies of the database schema are used in the redesign process.

A.True
B.False

Answer: B

Correct answer: False

Three copies are used, not two: the operational schema, which is left alone; a test copy on which the changes are proved against representative data; and a copy carrying the proposed new design. With only two, either the testing is done against live data or there is nowhere to develop the new structure.

Discuss in Forum

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