Database

Database

Database Redesign has 40 Questions

Which of the following SQL statements are helpful in database redesign?

Correlated subqueries only
EXISTS/NOT EXISTS expressions only
Both of the above are helpful
None of the above are helpful.
A correlated subquery is processed as a nested subquery.

True
False
What SQL command can be used to delete columns from a table?

MODIFY TABLE TableName DROP COLUMN ColumnName
MODIFY TABLE TableName DROP ColumnName
ALTER TABLE TableName DROP COLUMN ColumnName
ALTER TABLE TableName DROP ColumnName
A regular subquery is processed from the bottom up.

True
False
Database redesign is not terribly difficult if the:

database is structured.
database is well-designed.
database has no data.
database is relatively small.
Correlated subqueries are similar to a regular subquery.

True
False
Which SQL-92 standard SQL command can be used to change a table name?

RENAME TABLE
CHANGE TABLE
ALTER TABLE
None of the above is correct.
Database redesign is especially difficult if the database has no data.

True
False
The process of reading a database schema and producing a data model from that schema is known as:

data modeling.
database design.
reverse engineering.
None of the above is correct.
Some organizations take the stand that no application should ever employ the true name of a table.

True
False
Before any changes to database structure are attempted one should first:

clearly understand the current structure and contents of the database only.
test any changes on a test database only.
create a complete backup of the operational database only.
All of the above should be done.
The use of the double NOT EXISTS can be used to find rows that do not match some specified condition.

True
False
Which of the following modifications may not succeed?

Changing a column data type from char to date
Changing a column data type from numeric to char
Both of the above actions should succeed.
Neither of the above actions will succeed.
Although creating test databases is a critical and necessary job, there are few career opportunities in this area.

True
False
How can you find rows that do not match some specified condition?

EXISTS
Double use of NOT EXISTS
NOT EXISTS
None of the above is correct.
Because of the need for extensive knowledge of SQL, many database developers choose to automate the redesign process.

True
False
A regular subquery can be processed:

from the top down.
from the bottom up.
by nesting.
None of the above is correct.
The data model produced from the reverse engineering process does not include intersection table data.

True
False
What SQL command can be used to add columns to a table?

MODIFY TABLE TableName ADD COLUMN ColumnName
MODIFY TABLE TableName ADD ColumnName
ALTER TABLE TableName ADD COLUMN ColumnName
ALTER TABLE TableName ADD ColumnName
If a database is built correctly the first time, it will not have to be redesigned.

True
False
The EXISTS keyword will be true if:

any row in the subquery meets the condition only.
all rows in the subquery fail the condition only.
both of these two conditions are met.
neither of these two conditions is met.
The SQL-92 command to change a table name is RENAME TABLE.

True
False
Changing cardinalities in a database is:

a common database design task.
a rare database design task, but does occur.
a database design task that never occurs.
is impossible to do, so a new database must be constructed and the data moved into it.
Reverse engineering is the process of reading a database schema and producing a data model from that schema.

True
False
The NOT EXISTS keyword will be true if:

any row in the subquery meets the condition.
all rows in the subquery fail the condition.
both of these two conditions are met.
neither of these two conditions is met.
The data model produced from the reverse engineering process is a true logical model.

True
False
The data model that is produced from reverse engineering is:

a conceptual model.
an internal model.
a logical model.
None of the above is correct.
It is not easy to build a database correctly the first time.

True
False
To drop a column that is used as a foreign key, first:

drop the primary key.
drop the table containing the foreign key..
drop the foreign key constraint.
All of the above must be done.
Typically, there should be at least two different copies of the database schema used in the redesign process.

True
False
What SQL command will allow you to change the table STUDENT to add the constraint named GradeCheck that states that the values of the Grade column must be greater than 0?

ALTER TABLE STUDENT ALTER CONSTRAINT GradeCheck (Grade > 0);
ALTER TABLE STUDENT ADD CONSTRAINT GradeCheck (Grade > 0);
ALTER TABLE STUDENT ADD CONSTRAINT GradeCheck CHECK (Grade > 0);
None of the above is correct.
Information systems and organizations do not just influence each other; they create each other.

True
False
Which is not true of a correlated subquery?

EXISTS/NOT EXISTS is a form of a correlated subquery.
The processing of the SELECT statements is nested.
They can be used to verify functional dependencies.
They are very similar to a regular subquery.
Adding null columns to a table is straightforward.

True
False
A tool that can help designers understand the dependencies of database structures is a:

dependency graph.
data model.
graphical display.
None of the above is correct.
The NOT EXISTS keyword will be true if any row in the subquery meets the condition.

True
False
How many copies of the database schema are typically used in the redesign process?

One
Two
Three
Four
Dependency graphs are diagrams that consist of nodes and arcs that show the dependencies of a database.

True
False
Because of the importance of making data model changes correctly, many professionals are ________ about using an automated process for database redesign.

optimistic
skeptical
ambivalent
None of the above is correct.
The EXISTS keyword will be true if any row in the subquery meets the condition.

True
False