224 Chapter 8
A correlated subquery looks very different from a noncorrelated subquery.
FALSE
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.
FALSE
Adding new tables and relationships to a database is difficult.
FALSE
Although correlated subqueries are useful in database redesign, they cannot be used to verify functional dependencies.
FALSE
Database redesign is equally difficult regardless of whether or not the database has data in it.
FALSE
Database redesign is rarely needed because databases are usually built correctly the first time.
FALSE
Dependency graphs are graphical displays like bar charts.
FALSE
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.
FALSE
In a correlated subquery, the DBMS can run the lower SELECT statement by itself and then send the results to the upper SELECT statement.
FALSE
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.
FALSE
The NOT EXISTS keyword will be true if any row in the subquery fails to meet the condition.
FALSE
The RENAME TABLENAME command can be used to change table names.
FALSE
The data model produced by reverse engineering is a true conceptual schema.
FALSE
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.
FALSE
There are several difficulties with increasing cardinalities from 1:1 to 1:N, including preserving the existing relationships.
FALSE
To add a NULL column to a table, we simply use the MODIFY TABLE statement.
FALSE
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.
FALSE
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.
FALSE
Typically, there are at least four different copies of the database schema used in the redesign process.
FALSE
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.
TRUE
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.
TRUE
A means must be created to recover all test databases to their original state during the redesign testing process.
TRUE
Because EXISTS and NOT EXISTS are forms of correlated subqueries, the processing of the associated SELECT statements must be nested.
TRUE
Because of the need to know the functional dependencies in a database, it is a good idea to create a dependency graph.
TRUE
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.
TRUE
Converting date, money, or other more specific data types to char or varchar will usually succeed
TRUE
Correlated subqueries can be used to verify functional dependencies.
TRUE
Deleting tables and relationships is basically a matter of dropping foreign key constraints and then dropping the tables.
TRUE
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.
TRUE
EXISTS and NOT EXISTS are actually just another form of correlated subqueries.
TRUE
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.
TRUE
In a correlated subquery, the DBMS must run the lower SELECT statement as a process that is nested within the upper SELECT statement.
TRUE
In a correlated subquery, the same table is used in the upper and lower SELECT statements.
TRUE
In a real sense, information systems and organizations do not just influence each other, but rather they create each other.
TRUE
In order to minimize the need to change table names, some organizations have a policy that it is better to create a new table, map the data over to the new table and then delete the old table.
TRUE
In the SQL statement: SELECT S1.CustName, S1.SalesRepNo FROM SALES AS S1; the "S1" is called an alias.
TRUE
In the database redesign process, it is often useful to test whether certain conditions or assumptions are valid before proceeding with the redesign.
TRUE
SQL Server 2017 contains a system-stored procedure named sp_rename that can be used to change table names.
TRUE
The EXISTS keyword will be true if any row in the subquery meets the condition.
TRUE
The authors refer to the data model produced by reverse engineering as the RE data model.
TRUE
The continuous circular process of changes is known as the Systems Development Life Cycle (SDLC).
TRUE
The data model produced by reverse engineering may include some entities that should not appear in the data model.
TRUE
The design produced by reverse engineering may be described as a table-relationship diagram.
TRUE
The process of reading an actual database schema and producing a data model from that schema is called reverse engineering.
TRUE
The use of a doubly nested set of NOT EXISTS SELECT statements is a famous pattern in SQL use.
TRUE
There are no good SQL commands that can be used to change table names.
TRUE
There is a common trap in writing a correlated subquery, which will cause no rows to ever be displayed in the results.
TRUE
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.
TRUE
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.
TRUE
To drop a constraint, no preliminary steps are needed and we can simply use the ALTER TABLE DROP CONSTRAINT statement.
TRUE
To drop a nonkey column from a table, no preliminary steps are needed, and we can simply use the ALTER TABLE DROP COLUMN statement.
TRUE
When decreasing maximum cardinalities, there will always be data loss.
TRUE
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.
TRUE
When using a doubly nested set of NOT EXISTS SELECT statements, a row that does not match any row matches every row.
TRUE
When using queries with EXISTS and NOT EXISTS, the processing of the associated SELECT statements must be nested.
TRUE
