Test
214
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Preguntas del test (88)
1[blank_start]Many-to-many[blank_end], also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.
- AMany-to-many
2Fortunately, the problems inherent in the [blank_start]many-to-many[blank_end] relationship can easily be avoided by creating a composite entity.
- Amany-to-many
3The relational model's creator, E.F. Codd, used the term relation as a synonym for [blank_start]table[blank_end].
- Atable
4The [blank_start]1:M[blank_end] relationship is the relational database norm.
- A1:M
5Depending on the sophistication of the application development software, nulls can create problems when functions such as COUNT, AVERAGE, and SUM are used.
- AVerdadero
- BFalso
6A(n) [blank_start]equijoin[blank_end] links tables on the basis of an equality condition that compares specified columns of each table.
- Aequijoin
7In a relational model, if A determines B, C, and D, you write A = B, C, D.
- AVerdadero
- BFalso
8Referential [blank_start]integrity[blank_end] means that if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation.
- Aintegrity
9A [blank_start]relational schema[blank_end] is a textual representation of the database tables where each table is listed by its name follwed by the list of its attributes in paretheses.
- Arelational schema
10[blank_start]Outer[blank_end] joins are especially useful when you are trying to determine what value(s) in related tables cause(s) referntial integrity problems.
- AOuter
11Tables must have the same attribute characteristics (the columns and domains must be compatible) to be used in a UNION.
- AVerdadero
- BFalso
12In a database context, a(n) [blank_start]synonym[blank_end] indicates the use of different names to describe the same attribute.
- Asynonym
13When you define a table's primary key, the DBMS automatically creates a(n) [blank_start]unique[blank_end] index on the primary key column(s) you declared.
- Aunique
14Because the relational model uses attribute values to establish relationships among tables, many database users correctly assume that the term relation refers to such relationships.
- AVerdadero
- BFalso
15A proper understanding of the concept and use of keys in a relational database model is very important.
- AVerdadero
- BFalso
16Attribute A determines attribute B (that is, a is functionally [blank_start]dependent[blank_end] on A) if all of the rows in the table that agree in value for attribute A also agree in value for attribute B.
- Adependent
17In a natural join, the column on which the join was made occurs twice in the new table.
- AVerdadero
- BFalso
18DBMSs use indexes tor many different purposes.
- AVerdadero
- BFalso
19[blank_start]SELECT[blank_end] also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.
- ASELECT
20Each table in a relational database must have a primary key.
- AVerdadero
- BFalso
21If the attribute (B) is functionally dependent on a [blank_start]composite[blank_end] key (A) but not on any subset of that composite key, the attribute (B) is fully funcionally dependent on (A).
- Acomposite
22A(n) [blank_start]index[blank_end] is an ordered arrangement of keys and pointers.
- Aindex
23[blank_start]Logical[blank_end] data can have only a true or false (yes or no) values.
- ALogical
24Codd's rule of [blank_start]Guaranteed Access[blank_end] states that every value in a table is guaranteed to be accessible through a combination of table name, primary key value, and column name.
- AGuaranteed Access
25A [blank_start]candidate[blank_end] key can be described as a superkey without unnecessary attributes, that is, a minimal superkey.
- Acandidate
26If the foreign key contains eiher matching values or nulls, the table that makes use of that goreign key is said to exhibit [blank_start]referential[blank_end] integrity.
- Areferential
27[blank_start]JOIN[blank_end] is the real power behind the relational database. allowing the use of independent tables linked by common attributes.
- AJOIN
28Codd's rule of [blank_start]Logical Data Independence[blank_end] states: Application programs and ad hoc facilities are logically unaffected when changes are made to the table structures that preserve the original table values (changing order of columns or inserting columns).
- ALogical Data Independence
29Tables within a database share common attributes that enable the tables to be linked together.
- AVerdadero
- BFalso
30The [blank_start]1:1[blank_end] relationship should be rare in any relational database design.
- A1:1
31The index key can have multiple attributes, this is called a(n) [blank_start]composite[blank_end] index.
- Acomposite
32All RDBMSs enforce integrity rules automatically.
- AVerdadero
- BFalso
33The attribute B is [blank_start]functionally dependent on[blank_end] the attribute A if each value in column A determines one and only one value in column B.
- Afunctionally dependent on
34The relational operators have the property of [blank_start]closure[blank_end]; that is, the use of relational algebra operators on existing relations (Tables) produces new relations.
- Aclosure
35A(n) [blank_start]unique[blank_end] index is an index in which the index key can have only one pointer value (row) associated with it.
- Aunique
36DBMSs use indexes for many different purposes.
- AVerdadero
- BFalso
37The [blank_start]system catalog[blank_end] is actually a system-created database whose tables store the user/designer-created database characteristics and contents.
- Asystem catalog
38To avoid nulls, some designers use special codes, known as [blank_start]flags[blank_end], to indicate the absence of some value.
- Aflags
39A [blank_start]superkey[blank_end] is any key that uniquely identifies each row.
- Asuperkey
40A(n) [blank_start]data dictionary[blank_end] provides a detailed description of all tables found within the user.designer-created database.
- Adata dictionary
41in the context of a database table , the statement "A [blank_start]determines[blank_end] B" indicates that if you know the value of attribute A, you can look up the value of attribute B.
- Adetermines
42in a relational table, each column has a specific range of values known as the [blank_start]attribute[blank_end] domain.
- Aattribute
43The one-to-many (1:M) relationship is easily implemented in the relational model by putting the foreign key of the "1" side in the table of the "many: side as a primary key.
- AVerdadero
- BFalso
44A(n) [blank_start]natural[blank_end] join links tables by selecting only the rows with common values in their common attribute(s).
- Anatural
45As rare as 1:1 relationships should be, certain conditions absolutely require their use.
- AVerdadero
- BFalso
46A data dictionary contains metadata- data about data.
- AVerdadero
- BFalso
47The proper use of [blank_start]foreign[blank_end] keys is crucial to controlling data redundancy
- Aforeign
48The [blank_start]completeness[blank_end] constraint specifies whether each entity supertype occurence must also be a member of at least one subtype.
- Acompleteness
49Non-overlapping subtypes are subtypes that contain a(n) [blank_start]unique[blank_end] subset of the supertype entity set.
- Aunique
50The "[blank_start]security compliant[blank_end]" characteristic of a primary key states that: The selected primary key must not be composed of any attribute(s) that might be considered a security risk or violation. For example, using a Social Security number as a PK in an EMPLOYEE table is not a good idea.
- Asecurity compliant
51An [blank_start]entity supertype[blank_end] is a generic entity type that is related to one or more entity subtypes.
- Aentity supertype
52One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertypes.
- AVerdadero
- BFalso
53The property of subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype.
- AVerdadero
- BFalso
54Within a specialization hierarchy, a supertype can exist only within the context of a subtype.
- AVerdadero
- BFalso
55Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the [blank_start]M:N[blank_end] relationship.
- AM:N
56The most common design trap is known as a(n) [blank_start]fan trap[blank_end]
- Afan trap
57Disjoint subtypes are also known as [blank_start]non-overlapping[blank_end] subtypes.
- Anon-overlapping
58[blank_start]Redundant[blank_end] relationships occur when there are multiple relationship paths between related entities.
- ARedundant
59A [blank_start]fan trap[blank_end] occurs when you have one entity in two 1:M relationships to other entities, thus producing an association among the other entities that is not expressed in the model.
- Afan trap
60AT the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain a [blank_start]1:1[blank_end] relationship
- A1:1
61The relationships depicted within the specialization hierarchy are sometimes described in terms of "is-a" relationships.
- AVerdadero
- BFalso
62To model time-variant data, you must create a new entity in a M:N relationship with the orginial entity.
- AVerdadero
- BFalso
63The entity supertype contains the common charactersitics and the entity subtypes contain the unique characteristics of each entity subtype.
- AVerdadero
- BFalso
64Overlapping subtypes are subtypes that contain unique subset of the supertype entity set.
- AVerdadero
- BFalso
65A [blank_start]natural[blank_end] key is a real-world, generally accepted identifier used to uniquely identify real-world objects.
- Anatural
66The primary key's main function is to uniquely identify a(n) [blank_start]entity instance or row[blank_end] within a table.
- Aentity instance or row
67An entity supertype can have disjoint or overlapping entity subtypes
- AVerdadero
- BFalso
68[blank_start]Generalization[blank_end] is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.
- AGeneralization
69[blank_start]Foreign[blank_end] keys work with primary keys to properly implement relationships in the relational model.
- AForeign
70[blank_start]Partial[blank_end] completeness means that not every supertype occurrence is a member of a subtype.
- APartial
71Some designs use redundant relationships as a way to simplify the design
- AVerdadero
- BFalso
72The default comparison condition for the subtype discriminator attribute is the [blank_start]equality[blank_end] comparison.
- Aequality
73A(n) [blank_start]subtype discriminator[blank_end] is the attribute in the supertype entity that determines to which entity subtype each supertype occurence is related
- Asubtype discriminator
74The [blank_start]EERM[blank_end] is the result of adding more semantic constructs to the orginal entity relationship (ER) model.
- AEERM
75Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype.
- AVerdadero
- BFalso
76specialization is based on grouping [blank_start]unique[blank_end] characteristics and relationships of the subtypes.
- Aunique
77Connectivities and cardinalities are established by business rules.
- AVerdadero
- BFalso
78Identifying the attributes of the entities helps you better understand the [blank_start]relationships[blank_end] among entities.
- Arelationships
79The word "entity" in the ER model corresponds to a table
- AVerdadero
- BFalso
80Connectivities and cardinalities are usually based on [blank_start]business[blank_end] rules.
- Abusiness
81A weak entit has a primary key that is partially or totally derived from the parent entity in the relationship.
- AVerdadero
- BFalso
82Making sure all [blank_start]business rules[blank_end] are identified is a very important part of a database designer's job.
- Abusiness rules
83Relationships operate only in one direction.
- AVerdadero
- BFalso
84In an ER diagram, primary keys are usually bolded.
- AVerdadero
- BFalso
85In the Chen model, a multivalued attribute is connected to the owning entity with a double line.
- AVerdadero
- BFalso
86A [blank_start]weak[blank_end] entity has a primary key that is partially or totally derived from the parent entity in the relationship.
- Aweak
87a(n) [blank_start]strong[blank_end] relationship is also known as an identifying relationship
- Astrong
88[blank_start]Binary[blank_end] relationships are most common.
- ABinary
Información
- Descripción
- Test sobre 214, creado por Emily Noodles el 05/10/2017.
- Autor
- Emily Noodles
- Idioma
- English
- Visitas
- 0
- Valoración
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