Database Chapter 5 – Flashcards

The first step in representing entities using the relational model is to determine which identifier will be used as the key (T/F).

Relations should always be normalized to the highest degree possible (T/F).

If a weak entity is ID-dependent but not existence-dependent, it can be represented using the same techniques as a strong entity (T/F).

The key of the parent entity becomes part of the key of an ID-dependent entity (T/F).

From a pragmatic standpoint, the only important rule of normalization is that the determinant of every functional dependency must be a candidate key (T/F).

An entity needs to be examined according to normalization criteria before creating a table from it in the relational database design (T/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 (T/F).

By default, the identifier of the entity becomes the foreign key of the corresponding table (T/F).

The ideal primary key is short, numeric, and fixed (T/F).

A surrogate key is appropriate when the primary key of a table contains a lengthy text field (T/F).

One of the important properties of an attribute is whether or not it is required (T/F).

The technique for representing E-R relationships in the relational model is dependent on the minimum cardinality (T/F).

For a 1:1 relationship, the key of each table should be placed in the other table as a foreign key (T/F).

Relationships that are 1:1 do not require referential integrity constraints (T/F).

In certain circumstances, there may be a preference as to which table in a 1:1 relationship contains the foreign key (T/F).

When applied to 1:N relationships, the term "parent" refers to the many side of the relationship since a child may have many parents (T/F).

To represent a 1:N relationship in a relational model, the key of the entity on the one side of the relationship is placed as a foreign key in the entity on the many side of the relationship (T/F).

To represent a 1:N relationship in the relational model, the key of either entity may be placed as a foreign key in the other entity (T/F).

In the relational model, many to many relationships cannot be directly represented by relations the way 1:1 and 1:N relationships can (T/F).

To represent a M:N relationship in the relational model, an intersection relation is created to represent the relationship itself (T/F).

The key for an intersection relation is always the combination of the keys of the parent entities (T/F).

All recursive relationships are 1:1 (T/F).

Recursive relationships can be represented in the relational model using the same techniques that are used for binary relationships (T/F).

The first step in transforming an extended E-R model into a relational database design is to ________. A) create a table for each relationship B) evaluate the entities against the normalization criteria C) create a table for each entity D) remove any recursive relationships E) document referential integrity constraints

Each attribute of an entity becomes a(n) ________ of a table. A) column B) primary key C) foreign key D) alternate key E) B or D

The identifier of the entity becomes the ________ of the corresponding table. A) primary key B) foreign key C) supertype D) subtype E) either A or B

The ideal primary key is ________. A) short B) numeric C) fixed D) A and B E) A, B, and C

A surrogate key should be considered when ________. A) a relationship is M:N B) a composite key is required C) the key contains a lengthy text field D) the key contains a number E) an index needs to be created

Which of the following is not true about surrogate keys? A) They are identifiers that are supplied by the system, not the users. B) They have no meaning to the users. C) They are nonunique within a table. D) They can be problematic when combining databases. E) The DBMS will not allow their values to be changed.

One of the important properties of a column is whether or not it is ________. A) found in more than one entity B) required C) character or numeric D) subject to normalization E) subject to denormalization

In a relational database design, all relationships are expressed by ________. A) creating a primary key B) creating a foreign key C) creating a supertype D) creating a subtype E) creating a line between entities

Which of the following would be a reason to denormalize a relation? A) Relax security B) Lack of design time C) End user preference D) Improve performance E) None of the above

Which of the following is true about representing a weak entity with the relational model? A) If the weak entity is existence-dependent, the key of the parent must be part of the key of the weak entity. B) If the strong entity has a minimum cardinality of 1, the key of the weak entity must be part of the strong entity. C) If the weak entity is ID-dependent, the key of the weak entity must be part of the key of the parent entity. D) If the weak entity is ID-dependent, the key of the parent entity must be part of the key of the weak entity. E) If the parent entity is existence-dependent, then the minimum cardinality of the weak entity is zero.

Which of the following is true when representing a 1:1 binary relationship using the relational model? A) The key of the entity with the highest minimum cardinality must be placed in the other entity as a foreign key. B) The key of each entity must be placed in the other as a foreign key. C) The key of either entity is placed in the other as a foreign key. D) The key of the entity with the most attributes must be placed in the other entity as a foreign key. E) Both entities must have the same primary key.

Which of the following is the correct technique for representing a 1:N relationship in the relational model? A) The key of the entity on the one side is placed into the relation for the entity on the many side. B) The key of the child is placed into the relation of the parent. C) The key of either relation can be placed into the other relation. D) The key of the entity on the many side is placed into the relation for the entity on the one side. E) An intersection relation is created, and the keys from both parent entities are placed as keys in the intersection relation.

Which of the following is the correct technique for representing a M:N relationship using the relational model? A) An intersection relation is created, and the key of either entity is placed as a key in both the intersection relation and in the other relation. B) An intersection relation is created with a surrogate key, which is placed in each of the parent entities. C) An intersection relation is created, and the keys of both parent entities are placed as a composite key in the intersection relation. D) The key from either relation is placed as a foreign key in the other relation. E) None of the above

In many-to-many relationships in a relational database design, ________. A) the key of the child is placed as a foreign key into the parent B) the key of the parent is placed as a foreign key into the child C) the keys of both tables are placed in a third table D) the keys of both tables are joined into a composite key E) C and D

In many-to-many relationships in a relational database design, ________. A) the intersection table is ID-dependent on one of the parents B) the intersection table is ID-dependent on both of the parents C) the minimum cardinality from the intersection table to the parents is always M D) A and B E) B and C

In relational database design, ID-dependent entities are used to ________. A) represent 1:1 relationships B) represent 1:N relationships C) represent N:M relationships D) handle recursive relationships E) eliminate the need for weak entities being converted to tables.

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 ________. A) when the child entity is ID-dependent B) when the child entity is non-ID-dependent C) when the child entity has a 1:1 relationship with the parent entity D) when the child entity has a 1:N relationship with the parent entity E) when the child entity has a recursive relationship with the parent entity

When transforming an ID-dependent E-R data model relationship into a relational database design and the child entity is designed to use a surrogate key, then ________. A) the parent entity must also use a surrogate key B) the relationship remains an ID-dependent relationship C) the relationship changes to a non-ID-dependent relationship D) A and B E) A and C

What relationship pattern is illustrated in the following schema? PRODUCT (ProductID, Description) SUPPLIER (SupplierID, ContactName, PhoneNumber) PRODUCT_SUPPLIER (ProductID, SupplierID, Cost) ProductID in PRODUCT_SUPPLIER must exist in ProductID in PRODUCT SupplierID in PRODUCT_SUPPLIER must exist in SupplierID in PRODUCT A) Association relationship B) Intersection relationship C) Recursive relationship D) Strong entity relationship E) Supertype/subtype relationship

What relationship pattern is illustrated in the following schema? VEHICLE (VehicleID, Cost) CAR (VehicleID, NumberOfSeats) TRUCK (VehicleID, CargoCapacity) VehicleID in CAR must exist in VehicleID in VEHICLE VehicleID in TRUCK must exist in VehicleID in VEHICLE A) Association relationship B) Intersection relationship C) Recursive relationship D) Strong entity relationship E) Supertype/subtype relationship

Which of the following is not true about representing subtypes in a relational database design? A) One table is created for the supertype and one for each subtype. B) All of the attributes of the supertype are added to the subtype relations. C) The key of the supertype is made the key of the subtypes. D) A subtype and its supertype are representations of the same underlying table. E) An instance of the supertype may be related to one instance each of several subtypes.

What relationship pattern is illustrated in the following schema? EMPLOYEE (EmployeeID, OfficePhone, Manager) Manager in EMPLOYEE must exist in EmployeeID in EMPLOYEE A) Association relationship B) Intersection relationship C) Recursive relationship D) Strong entity relationship E) Supertype/subtype relationship

Which of the following is not true of recursive relationships? A) When the recursive relationship is M:N, an intersection table is created. B) The rows of a single table can play two different roles. C) The techniques for representing the tables are the same as for non-recursive relationships except the rows are in the same table. D) Recursive relationships can be 1:1, 1:N, or M:N relationships. E) Even when the relationship is 1:N, a new table must be defined to represent the relationship.

Which of the following is not true about surrogate keys? A) They are identifiers that are supplied by the system, not the users. B) They have no meaning to the users. C) They are nonunique within a table. D) They can be problematic when combining databases. E) The DBMS will not allow their values to be changed.