Deck 8: Database Redesign

Question 1

Although correlated subqueries are useful in database redesign,they cannot be used to verify functional dependencies.

Answer 1

False

Question 2

A doubly nested set of NOT EXISTS SELECT statements can be used to find rows that meet some specified condition for every row in a table.

Answer 2

True

Question 3

In a correlated subquery,the same table is used in the upper and lower SELECT statements.

Answer 3

True

Question 4

Database redesign is rarely needed because databases are usually built correctly the first time.

Question 5

The use of a doubly nested set of NOT EXISTS SELECT statements is a famous pattern in SQL use.

Question 6

Correlated subqueries can be used to verify functional dependencies.

Question 7

In the SQL statement:
SELECT S1.CustName,S1.SalesRepNo FROM SALES S1;
the "S1" is called an alias.

Question 8

EXISTS and NOT EXISTS are actually just another form of correlated subqueries.

Question 9

In a correlated subquery,the DBMS can run the lower SELECT statement by itself and then send the results to the upper SELECT statement.

Question 10

In the database redesign process,two SQL tools are useful for testing whether or not certain conditions or assumptions are valid: uncorrelated subqueries and EXISTS/NOT EXISTS.

Question 11

There is a common trap in writing a correlated subquery,which will cause no rows to ever be displayed in the results.

Question 12

Database redesign is equally difficult whether or not the database has data in it.

Question 13

In a correlated subquery,the DBMS must run the lower SELECT statement as a process that is nested within the upper SELECT statement.

Question 14

In a real sense,information systems and organizations do not just influence each other,but rather they create each other.

Question 15

A continuous circular process of changes in user behaviors and change in the information systems they use is a natural outcome of information system use.

Question 16

When using queries with EXISTS and NOT EXISTS,the processing of the associated SELECT statements must be nested.

Question 17

Because EXISTS and NOT EXISTS are forms of correlated subqueries,the processing of the associated SELECT statements must be nested.

Question 18

In the database redesign process,it is often useful to test whether certain conditions or assumptions are valid before proceeding with the redesign.

Question 19

A correlated subquery looks very different from a noncorrelated subquery.

Question 20

The continuous circular process of changes is known as the Systems Development Life Cycle (SDLC).

Question 21

The NOT EXISTS keyword will be true if any row in the subquery fails to meet the condition.

Question 22

A means must be created to recover all test databases to their original state during the redesign testing process.

Question 23

Typically,there are at least four different copies of the database schema used in the redesign process.

Question 24

There is no good SQL command that can be used to change table names.

Question 25

The authors refer to the data model produced by reverse engineering as the RE data model.

Question 26

In order to minimize the need to change table names,some organizations have a policy that no user or application should ever employ the true name of a table,but use views as table aliases instead.

Question 27

SQL Server 2014 contains a system-stored procedure named sp_rename that can be used to change table names.

Question 28

A doubly nested set of EXISTS SELECT statements can be used to find rows that meet some specified condition for every row in a table.

Question 29

Changing table names is complicated by the fact that constraints and triggers are often associated with the table and will also need to be changed.

Question 30

SQL contains an SQL command RENAME TABLENAME that can be used to change table names.

Question 31

Dependency graphs are graphical displays like bar charts.

Question 32

The use of a doubly nested set of NOT EXISTS SELECT statements is so rare that even if you are a professional database developer you will probably never see it used.

Question 33

The data model produced by reverse engineering may include some entities that should not appear in the data model.

Question 34

The process of reading an actual database schema and producing a data model from that schema is called reverse engineering.

Question 35

When using a doubly nested set of NOT EXISTS SELECT statements,a row that does not match any row matches every row.

Question 36

Because of the need to know the functional dependencies in a database,it is a good idea to create a dependency graph.

Question 37

The design produced by reverse engineering may be described as a table-relationship diagram.

Question 38

Even if an organization has a very large database,it will be possible to make a complete backup copy of the operational database prior to making structural changes.

Question 39

The data model produced by reverse engineering is a true conceptual schema.

Question 40

The EXISTS keyword will be true if any row in the subquery meets the condition.

Question 41

To drop a foreign key column from a table,no preliminary steps are needed and we can simply use the ALTER TABLE DROP COLUMN statement.

Question 42

To drop a constraint,no preliminary steps are needed and we can simply use the ALTER TABLE DROP CONSTRAINT statement.

Question 43

Deleting tables and relationships is basically a matter of dropping foreign key constraints and then dropping the tables.

Question 44

To drop a nonkey column from a table,no preliminary steps are needed and we can simply use the ALTER TABLE DROP COLUMN statement.

Question 45

In the database redesign process,before proceeding with the redesign it is often useful to ________.

A)check whether certain conditions or assumptions about the data are valid
B)find out why the design was not done properly the first time
C)stop information systems and users from influencing each other
D)set standards for user behavior

Question 46

Adding new tables and relationships to a database is difficult.

Question 47

To drop a primary key column from a table the primary key constraint must first be dropped,but this does not require that related foreign keys based on the column be dropped.

Question 48

Depending on the DBMS,when changing the minimum cardinality on the parent side from zero to one,the foreign key constraint that defines the relationship may have to be dropped before the change is made and re-added afterwards.

Question 49

Converting date,money,or other more specific data types to char or varchar will usually succeed.

Question 50

There are several difficulties with increasing cardinalities from 1:1 to 1:N,one of which is preserving the existing relationships.

Question 51

Database redesign is fairly easy when ________.

A)information systems and organizations influence each other
B)the design was done correctly the first time
C)there is no data in the database
D)good backups of the database are available

Question 52

When increasing cardinalities from 1:N to N:M,we basically create a new intersection table,fill it with data and drop the old foreign key.

Question 53

Which of the following is not a possible step in the database redesign process?

A)Checking whether certain conditions or assumptions about the data are valid
B)Reverse engineering the data model
C)Revising user account name policies
D)Maintaining backups of the existing database

Question 54

In the database redesign process,an SQL tool that is useful for testing whether or not certain conditions or assumptions are valid is ________.

A)UPDATE
B)DROP TABLE
C)CREATE TRIGGER
D)NOT EXISTS

Question 55

When decreasing maximum cardinalities,there will always be data loss.

Question 56

In a correlated subquery of a database that has tables TableOne and TableTwo,if table TableOne is used in the upper SELECT statement,then which table is used in the lower SELECT statement?

A)TableOne
B)TableTwo
C)Both TableOne and TableTwo
D)Either TableOne or TableTwo

Question 57

To add a NULL column to a table,we simply use the MODIFY TABLE statement.

Question 58

If a DEFAULT constraint is included when a new column is added to a table,the default value is only applied to new rows and not to the existing rows at the time the new column is added.

Question 59

To change the minimum cardinality on the parent side from zero to one,the foreign key,which would have been NULL,must be changed to NOT NULL.

Question 60

To add a NOT NULL column to a table,we first add a NULL column,then we insert values into every row,and finally we change the NULL constraint to NOT NULL.

Question 61

In a doubly nested set of NOT EXISTS SELECT statements,________.

A)if a row does not not match any row,then it matches every row
B)if a row matches any row,then it matches every row
C)if a row does not match any row,then it does not match every row
D)if a row matches any row,then it does not match every row

Question 62

The data model produced by reverse engineering is a(n)________.

A)conceptual schema
B)internal schema
C)dependency graph
D)table-relationship diagram

Question 63

A doubly nested set of NOT EXISTS SELECT statements is ________.

A)a famous pattern in SQL
B)regularly used
C)rarely used to nonexistent in the real world
D)Both A and B are correct

Question 64

When running an SQL query that uses EXISTS,the EXISTS keyword will be true if ________.

A)any row in the subquery meets the condition
B)all rows in the subquery meet the condition
C)no row in the subquery meets the condition
D)any row in the subquery fails to meet the condition

Question 65

To add a NULL column to a table,we ________.

A)use the REVISE TABLE command
B)use the ALTER TABLE command
C)use the MODIFY TABLE command
D)create a new table with the NULL column,move the other data,and drop the old table

Question 66

If a DEFAULT constraint is included when a new column is added to a table,the default value is applied to ________.

A)all existing rows at the time the column is added
B)all new rows
C)all new rows but only after the UPDATE command is issued
D)Both A and B are correct

Question 67

When running a correlated subquery,the DBMS ________.

A)runs the lower SELECT statement by itself and then sends the results to the upper SELECT statement.
B)runs the upper SELECT statement by itself and then sends the results to the lower SELECT statement.
C)alternates running the lower SELECT statement with running the upper SELECT statement based on each result of the lower SELECT statement
D)Either A or B may be used depending on the query.

Question 68

In order to make sure the database redesign is working properly during the redesign testing process,a means must be created to ________.

A)reverse engineer all test databases
B)graph dependencies in all test databases
C)recover all test databases to their original state
D)re-interview all relevant users

Question 69

The data model produced by reverse engineering is not truly a logical model because it will contain ________.

A)tables for strong entities
B)supertype/subtype tables
C)tables for ID-dependent entities
D)intersection tables

Question 70

In the SQL statements SELECT C1.CustName,C1.SalesRepNo
FROM CUSTOMER C1;
The "C1" is called a(n)________.

A)term
B)alias
C)convention
D)label

Question 71

A dependency graph should include all of the following except ________.

A)tables
B)views
C)triggers
D)DEFAULT values

Question 72

Which of the following different copies of the database schema is typically not used in the database redesign process?

A)Small test database
B)Data warehouse database
C)Operational database
D)Large test database

Question 73

When running a correlated subquery,the DBMS always uses ________.

A)regular processing
B)nested processing
C)"quick and dirty" processing
D)SQL-92 processing

Question 74

The process of reading an actual database schema and producing a data model from that schema is called ________.

A)data modeling
B)data engineering
C)reverse engineering
D)schema modeling

Question 75

Which of the following SQL statements is a correctly stated correlated subquery?

A)SELECT C1.CustName,C1.SalesRepNo
FROM CUSTOMER C1
WHERE C1.SalesRepNo IN
(SELECT S1.SalesRepNo
FROM SALESREP S1
WHERE S1.RepName = 'Smith');
B)SELECT C1.CustName,C1.SalesRepNo
FROM CUSTOMER C1
WHERE C1.SalesRepNo IN
(SELECT S1.SaleRepNo
FROM SALESREP S1
WHERE S1.RepName = 'Smith')
AND C1.SalesRepNo=S1.SalesRepNo);
C)SELECT C1.CustName,C1.SalesRepNo
FROM CUSTOMER C1
WHERE C1.SalesRepNo IN
(SELECT S1.SaleRepNo
FROM SALESREP S1
WHERE S1.RepName = 'Smith')
AND C1.SalesRepNo<>S1.SalesRepNo);
D)SELECT C1.CustName,C1.SalesRepNo
FROM CUSTOMER C1
WHERE C1.SalesRepNo IN
(SELECT C2.SaleRepNo
FROM CUSTOMER C2
WHERE C1.SalesRepNo=C2.SalesRepNo);
AND C1.OrderNo<>C2.OrderNo);

Question 76

SQL queries that use EXISTS and NOT EXISTS are ________.

A)normal subqueries
B)correlated subqueries
C)uncorrelated subqueries
D)constraint dependent subqueries

Question 77

Because of the need to know the functional dependencies in a database,it is a good idea to create a(n)________.

A)conceptual schema
B)internal schema
C)dependency graph
D)table-relationship diagram

Question 78

To change a table name,we ________.

A)use the SQL RENAME TABLE command
B)use the SQL ALTER TABLENAME command
C)use the SQL MODIFY TABLENAME command
D)create a new table,move the data,and drop the old table

Question 79

When making any change to the database structure,we may need to check for effects of the change on any of the following except ________.

A)data
B)foreign keys
C)ad-hoc SQL queries
D)triggers

Question 80

When running an SQL query that uses NOT EXISTS,the NOT EXISTS keyword will be true if ________.

A)any row in the subquery meets the condition
B)all rows in the subquery meet the condition
C)no row in the subquery meets the condition
D)any row in the subquery fails to meet the condition