Pregunta 1
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1) An ERM is dependent on the database type.
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2) The word “entity” in the ER model corresponds to a table.
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3) The Crow’s Foot model is less implementation-oriented than the Chen model.
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4) The ER diagram represents the conceptual database as viewed by the end user.
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5) The ER model refers to a specific table row as an entity instance.
Pregunta 6
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6) In both the Chen and Crow’s Foot models, an entity is represented with a rectangle containing the entity’s name.
Pregunta 7
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7) The ER model refers to a specific table row as an entity occurrence.
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8) Attributes are types of entities.
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9) In the original Chen model, each attribute is represented using an oval with the
attribute name connected to the entity with a line.
Pregunta 10
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10. Software vendors have adopted the Chen representation because of its compact
representation.
Pregunta 11
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11) Attributes have a domain that specifies the data type of the attribute.
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12) Attributes cannot share a domain.
Pregunta 13
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13) In an ER diagram, primary keys are usually bolded.
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14. Ideally, a primary key is composed of several attributes.
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15. A composite identifier is a primary key composed of more than one attribute.
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16. All attributes are either simple or composite.
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17) All simple attributes are also single-valued.
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18) In the Chen model, a multivalued attribute is connected to the owning entity
with a double line.
Pregunta 19
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19) The DBMS can easily handle multivalued attributes.
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20) Derived attributes are stored in a special database table.
Pregunta 21
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21) A relationship is identified by a name that describes the relationship.
Pregunta 22
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22) Cardinality expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.
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23) In Chen notation, there is no way to represent cardinality.
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24) Connectivities and cardinalities are established by business rules.
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25) A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity.
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26) You should always load data from the 1 side of a 1:M relationship.
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27) A weak entity has a primary key that is partially or totally derived from the parent entity in the relationship
Pregunta 28
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28. The existence of a mandatory relationship indicates that the minimum cardinality is 0 or 1 for the mandatory entity.
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29) Relationships operate only in one direction.
Pregunta 30
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30. A recursive relationship is one in which a relationship can exist between occurrences of the same entity set