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Question
Why do we need to optimize a DBMS with SQL performance tuning, even though they automatically optimize SQL queries?Answer
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Related questions
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Unique values can be better managed when they are________ , because the database can use internal routines to implement a counter-style attribute that automatically increments values with the addition of each new row.
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The____________ is the result of adding more semantic constructs to the original entity relationship (ER) model.
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A dependency of one nonprime attribute on another nonprime attribute is a partial dependency.
a. True
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A determinant is any attribute whose value determines other values within a column.
a. True
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It is possible for a table in 2NF to exhibit transitive dependency, where the primary key may rely on one or more nonprime attributes to functionally determine other nonprime attributes.
a. True
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A table is in 2NF if it is in 1NF, and it includes no partial dependencies.
a. True
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Converting a database format from 1NF to 2NF is a complex process.
a. True
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In the context of partial dependencies, data redundancies occur because every row entry requires duplication of data.
a. True
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Repeating groups must be eliminated by ensuring that each row defines a single entity.
a. True
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A table is in BCNF if every determinant in the table is a foreign key.
a. True
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Normalization is a process that is used for changing attributes to entities.
a. True
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From a data modeling point of view, ___________--data refer to data whose values change over time and for which one must keep a history of the data changes.
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The " __________________" characteristic of a primary key states that the primary key must uniquely identify each entity instance, must be able to guarantee unique values, and must not contain nulls.a. unique valuesb. nonintelligentc. preferably single-attributed. security-complaint
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A primary key's main function is to uniquely identify a(n)_______________ within a table.a. attributeb. entity instance or rowc. entity subtyped. natural key or identifier
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An entity cluster is formed by combining multiple interrelated entities into_______________ .a. a single abstract entity objectb. multiple abstract entity objectsc. a single entity objectd. multiple entity objects
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______________is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.a. Specializationb. Generalizationc. Normalizationd. Total completeness
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Overlapping subtypes are subtypes that contain_______--- subsets of the supertype entity set.a. nullb. exclusivec. solitaryd. nonunique
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Nonoverlapping subtypes are subtypes that contain a(n)________ subset of the supertype entity set.a. entityb. subtypesc. uniqued. nonunique
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Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness?
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b. Supertype has optional subtypes.
c. Subtype discriminators cannot be null.
d. Subtype does not have a supertype.
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At the implementation level, the supertype and its subtype(s) depicted in a specialization hierarchy maintain a(n)__________ relationship.a. self-referencingb. 1:1c. 1:Md. M:N
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What components should an implementation-ready data model contain?
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In_________________________ , a threepronged symbol represents the "many" side of the relationship.
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Each row in a relation is called a(n)_______________ .
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A(n) ________________is a brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization.
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A(n)__________ is a restriction placed on the data.a. attribute b. entityc. relationship d. constraint
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The hierarchical model is software-independent.a. Trueb. False