all hw questions
The first step in transforming an extended E-R model into a relational database design is to ________.
- remove any recursive relationships
For the M-O (parent mandatory, child optional) case, what action(s) should be taken to ensure minimum cardinality is maintained?
Both Define referential integrity constraint from child to parent and Make foreign key NOT NULL are correct
Which of the following is not true about representing subtypes in a relational database design?
All attributes of the supertype are added to the subtype relations.
Which of the following is not a step in the database design process?
Create constraints and triggers
A data constraint is a limitation on data values.
t
A referential integrity constraint policy that insures that all rows containing a foreign key value in a table are eliminated from the table when the row containing the corresponding primary key value in a parent table is eliminated from the database is called cascading deletes.
t
A surrogate key is a unique, system-supplied identifier often used as the primary key of a table.
t
A surrogate key is appropriate when the primary key of a table contains a lengthy text field.
t
A surrogate key should be considered when the key contains a lengthy text field.
t
In a 1:1 relationship, the foreign key is defined as an alternate key to make the DBMS enforce uniqueness.
t
One of the important properties of a column is whether or not it can have a NULL value.
t
SQL triggers use the ANSI SQL keywords BEFORE, INSTEAD OF, and AFTER.
t
When transforming supertype/subtype entities into a relational database design, the key of the supertype table is placed into the subtype table typically as the key.
t
Which of the following is not true of a MUST constraint?
It can be expressed directly in a relational model.
Which of the following is not true about a NULL attribute?
It must have a default value specified.
Which of the following is not true of recursive relationships?
When the relationship is 1:N, a new table must be defined to represent the relationship.
The binary constraint MUST COVER indicates that ________.
a binary relationship includes a set of value combinations that must all occur in a ternary relationship
The binary constraint MUST NOT indicates that ________.
a binary relationship includes value combinations that must not occur in a ternary relationship
Which of the following is not true for an ideal primary key?
a composite of several long attributes
Many-to-many relationships are represented by ________.
an intersection table which has 1:N relationships with the two tables
A referential integrity constraint policy that insures that all rows containing a foreign key value in a table are eliminated from the table when the row containing the corresponding primary key value in a parent table is eliminated from the database is called ________.
cascading deletes
A referential integrity constraint policy that insures that foreign key values in a table are correctly maintained when there is a change to the primary key value in the parent table is called ________.
cascading updates
Each attribute of an entity becomes a(n) ________ of a table.
column
A default value is the value the user enters into the row the first time the user enters data.
f
A foreign key is a key that does not belong in any table.
f
A null value is an attribute value that has been set to zero.
f
A referential integrity constraint policy that insures foreign key values in a table are correctly maintained when there is a change to the primary key value in the parent table is called a cascading insertion.
f
A stored program that is stored within the database and compiled when used is called a trigger.
f
An entity needs to be examined according to normalization criteria before creating a table from it in the relational database design.
f
An intersection table can have additional attributes besides the keys of its parent tables.
f
When the parent entity has a surrogate key, the enforcement actions are the same for both parent and child.
f
When transforming supertype/subtype entities into a relational database design, all of the attributes for the supertype table are placed into the subtype relations.
f
In relational database design, ID-dependent entities are not used to ________.
represent relationships where the child identifier does not include the key of the parent
Which of the following is not true about N:M recursive relationships?
Both Since it is a recursive relationship, an intersection table is not needed and The foreign keys in the intersection table can't refer to the same attribute in the parent table are correct.
In a supertype-subtype structure, discriminator attributes ________.
Both cannot be represented in a relational design and require application logic to determine which subtypes correspond to a specific supertype instance are correct
In many-to-many relationships between strong entities in a relational database design, which of the following is not true?
The intersection table is ID-dependent on one of the parents
A surrogate key should be considered when ________.
The key contains a lengthy text field
When transforming supertype/subtype entities into a relational database design, an entity is created for the supertype only.
f
When transforming an ID-dependent E-R data model relationship into a relational database design, the referential integrity constraints should allow ________.
parent updates to cascade
The identifier of the entity becomes the ________ of the corresponding table.
primary key
Because SQL statements are set-oriented, whereas programs are element-oriented, the results of SQL statements used in programs are treated as ________.
pseudofiles
A key of an intersection table is always the combination of the keys of both parents.
t
All identifying relationships are 1:N.
t
An ID-dependent table can be used to represent multivalued attributes.
t
An SQL virtual table is called a view.
t
An intersection table is always ID-dependent on both of its parent tables.
t
Association tables sometimes connect more than two entities.
t
Cascading deletions are generally not used with relationships between strong entities.
t
Data values to be added to a table are specified by using the VALUES clause.
t
Each entity in the extended E-R model is represented as a table in the relational database design.
t
If the parent is required, then a new child row must be created with a valid foreign key value.
t
In 1:N relationships, the table on the "many" side is called the child.
t
In 1:N relationships, the table on the "one" side is called the parent.
t
In a relational database design, all relationships are expressed by creating a foreign key.
t
In many-to-many relationships in a relational database design, the primary keys of both tables are joined into a composite primary key in the intersection table.
t
In representing a 1:N relationship in a relational database design, the key of the table representing the parent entity is placed as a foreign key in the table representing the child entity.
t
Like all ID-dependent relationships, the parents of an association table are required.
t
One of the important properties of an attribute is whether or not it is required.
t
Recursive M:N relationships are represented with an intersection table that shows pairs of related rows from a single table.
t
Referential integrity constraints should disallow adding a new row to a child table when the foreign key does not match a primary key value in the parent table.t
t
The first step in the database design process is to create tables and columns from entities and attributes.
t
The ideal primary key is short, numeric, and fixed.
t
The last step in creating a table is to verify table normalization.
t
The values of a surrogate key have no meaning to the users.
t
To represent a 1:1 binary relationship in a relational database design, the key of one table is placed into the second table.
t
To represent an N:M relationship in a relational database design, a table is created between the two tables to represent the relationship itself.
t
To represent an N:M relationship in a relational database design, an intersection table is created.
t
To represent an N:M relationship in a relational database design, in essence it is reduced to two 1:N relationships.
t
When creating a table for an ID-dependent entity, both the key of the parent and the key of the entity itself must appear in the table.
t
When placing a foreign key for a 1:1 relationship, the key of either table can be used as the foreign key in the other table.
t
When the child entity is required (M) in a relationship, there needs to always be at least one child row for each parent row.
t
When the parent entity is required (M) in a relationship, every row of the child table must have a valid, non-null value of the foreign key.
t
When transforming an ID-dependent E-R data model relationship into a relational database design where the child entity is designed to use a surrogate key, the relationship changes to a weak but not ID-dependent relationship.
t
When transforming an extended E-R model into a relational database design, recursive relationships are treated fundamentally the same as other HAS-A relationships.
t
To represent a one-to-many relationship in a relational database design, ________.
the key of the parent is placed as a foreign key into the child
In many-to-many relationships in a relational database design, ________.
the keys of both tables are placed in a third table
When representing a one-to-many relationship in a relational database design, ________.
the parent is always on the one side of the "one-to-many" relationship
When transforming an E-R data model into a relational database design, the key of the parent entity should be placed as part of the primary key into the child entity ________.
when the child entity is ID-dependent
It is easy to enforce the referential integrity actions for N:M relationships.
f
The design transformation for all IS-A relationships can be summarized by the phrase "place the key of the parent table in the child table."
f
To represent a 1:N relationship in a relational database design, an intersection table is created.
f
To represent a one-to-many relationship in a relational database design, the key of the child table is placed as a foreign key into the other table.
f
To represent an IS-A relationship in a relational database design, the IS-A relationship must be converted into a HAS-A relationship.
f
When creating a relational database design from E-R diagrams, first create a relation for each relationship.
f
When creating a table in the relational database design from an entity in the extended E-R model, the attributes of the entity become the rows of the table.
f
A referential integrity constraint policy that guarantees that a row in a parent table always has a required entry in a child table ________.
-is enforced in most DBMS products
Four uses for ID-dependent entities include all of the following except ________.
-storing multivalued attributes
Which of the following is not true about surrogate keys?
They are non-unique within a table.
A stored program that is attached to the database is called ________.
a stored procedure
Because SQL statements are table-oriented, whereas programs are element-oriented, the results of SQL statements used in programs are accessed using ________.
an SQL cursor
In a relational database design, all relationships are expressed by ________.
creating a foreign key
When representing a 1:1 relationship in a relational database design, ________.
the key of either table may be placed as a foreign key into the other
When the key of one table is placed into a second table to represent a relationship, the key is called a relational key in the second table.
f
By default, the identifier of the entity becomes the foreign key of the corresponding table.
f
Cascading deletions are generally not used with relationships for weak child entities.
f
Data types are consistent across all DBMS products.
f
Deciding whether or not an attribute is required is determined during the data modeling phase.
f
Discriminator attributes can be represented in relational designs.
f
In a 1:N relationship, the term parent refers to the table on the "many" side of the relationship.
f
In representing a 1:N relationship in a relational database design, the key of the table representing the entity on the "many" side is placed as a foreign key in the table representing the entity on the "one" side of the relationship.
f
