DBMS CH06 – Flashcards
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The binary constraint MUST NOT indicates that ________.
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a binary relationship includes value combinations that must not occur in a ternary relationship
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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 ________.
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the relationship changes to a non-ID-dependent relationship
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In relational database design, ID-dependent entities are used to ________.
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handle associative relationships
handle multivalued attributes
represent N:M relationships
handle archetype/instance relationships
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Which of the following is not a step in the database design process?
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Create constraints and triggers
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The binary constraint MUST COVER indicates that ________.
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a binary relationship includes a set of value combinations that must all occur in a ternary relationship
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The ideal primary key is ________.
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numeric
short
fixed
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To represent a one-to-many relationship in a relational database design ________.
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the key of the parent is placed as a foreign key into the child
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The first step in transforming an extended E-R model into a relational database design is to ________.
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create a table for each entity
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Each attribute of an entity becomes a(n) ________ of a table.
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column
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Which of the following is not true of ternary relationships?
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Must involve at least one M:N relationship
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A referential integrity constraint policy that insures that all rows containing a particular 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 ________.
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cascading deletes
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Which of the following is not true about surrogate keys?
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They are nonunique within a table.
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To which of the following actions are referential integrity constraints not applied?
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create
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In a supertype-subtype structure, discriminator attributes ________.
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cannot be represented in a relational design
require application logic to determine which subtypes correspond to a specific supertype instance
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When representing a one-to-many relationship in a relational database design ________.
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the parent is always on the one side of the 'one-to-many' relationship
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Which of the following is not true of recursive relationships?
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Even when the relationship is 1:N, a new table must be defined to represent the relationship.
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Which of the following is not true about representing subtypes in a relational database design?
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All of the attributes of the supertype are added to the subtype relations.
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One of the important properties of a column is whether or not it is ________.
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required
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When transforming an ID-dependent E-R data model relationship into a relational database design, the referential integrity constraints should allow ________.
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parent updates to cascade
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The identifier of the entity becomes the ________ of the corresponding table.
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primary key
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A surrogate key should be considered when ________.
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the key contains a lengthy text field
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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 ________.
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when the child entity is ID-dependent
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When transforming an ID-dependent E-R data model relationship into a relational database design and the parent entity has a surrogate primary key and the child entity has a data identifier, then the primary key of the child table should be ________.
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the parent's surrogate key + the child's data key
the parent's surrogate key + a surrogate key in the child
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Many-to-many relationships are represented by ________.
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an intersection table which has 1:N relationships with the two tables
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A referential integrity constraint policy that guarantees that a row in a parent table always has a required entry in a child table ________.
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is known as a minimum cardinality enforcement action
needs to be documented by the database development team
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In many-to-many relationships in a relational database design ________.
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the keys of both tables are placed in a third table
the keys of both tables are joined into a composite key
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In a relational database design, all relationships are expressed by ________.
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creating a foreign key
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When representing a 1:1 relationship in a relational database design ________.
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the key of either table may be placed as a foreign key into the other
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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 ________.
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cascading updates
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In many-to-many relationships in a relational database design ________.
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the intersection table is ID-dependent on both of the parents
the minimum cardinality from the intersection table to the parents is always 1
