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37 Cards in this Set
- Front
- Back
- 3rd side (hint)
what are the advantages of using DBS over file based systems for data storage? |
-control of data redundancy -preserve data consistency -sharing of data ( easier ) -improve security -increase productivity -support of multiple views of data - improve maintenance through data independence -increase concurrency -improve backup and recovery |
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what are the disadvantages of using DBS for storing data? |
-complexity -size -cost of DBMS -additional hardware costs -cost of conversion performance -overhead for providing generality, security, concurrency control, recovery, and integrity functions -higher impact of a failure |
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list the 3 generations of Database Systems? |
1 hierarchical/network 2 relational 3 object oriented/object relational |
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What are the four major issues in databases? |
(RISC) Recovery, Integrity, Security, and Concurrency |
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What are the advantages of the ANSI-SPACR database architecture? |
logical/physical data independence |
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what is a data model? |
a collection of concepts describing data |
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attribute
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A property of an entity or a relationship type |
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system catalog |
a repository of information describing the data in the database. Accessible to all users as well as DBMS |
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view |
defines what is required of a database system from the perspective of a particular job role or enterprise application area |
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schema |
a description of a database. |
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distributed database |
a logically interrelated collection of shared data (and a description of this data) physically distributed over a computer network
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SOA |
simple object access
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web service |
a software system designated to support inter-operable machine-to-machine interaction over a network |
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Integrity constraint |
consistency rules that the database is not permitted to violate |
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Degree |
the number of attributes a relation contains |
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Cardinality |
describes the maximum number of possible relationship occurrences for an entity participating in a given relationship type
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Cartesian product |
a table containing all the possible pairs of rows from 2 tables
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Primary key |
A candidate key that is selected to uniquely identify each occurrence of an entity type |
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candidate key |
minimal set of attributes that uniquely identifies each occurrence of an entity type |
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composite key |
a candidate key that consists of two or more attributes |
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foreign key |
an attribute, or set of attributes, within one relation that matches the candidate key of some ( possibly the same) relation |
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define attribute domain |
the set of allowable values for one or more attributes |
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example of attribute domain |
number of rooms associated with a property is between 1-15. (the term would be for labeling this range of possible values) |
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Describe: simple/single-valued attribute |
An entity's attribute composed of a single component
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Example: simple/ single-valued attribute |
Employee with SSN 123-45-6789
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Describe: composite attribute |
an attribute composed of multiple components, each with an independent existence
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Example: composite attribute |
Address, Name (can be nested)
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Describe: multi-valued attribute |
an attribute that holds multiple values for each occurrence of an entity type |
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Example: multi-valued attribute
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Previous jobs for an employee |
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What is a recursive relationship? |
A relationship type where the same entity participates more than once in different roles
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What is a Strong Entity type? |
Entity type that is not existence-dependent on some other entity type. |
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What is a Weak Entity type? |
Entity type that is existence-dependent on some other entity type. |
Identified by a partial key of the weak entity type and by the primary key of the strong entity type they are related to |
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What is a fan trap?
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Where a model represents a relationship between entity types, but pathway between certain entity occurrences is ambiguous |
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What is a chasm trap? |
Where a model suggests the existence of a relationship between entity types, but pathway does not exist between certain entity occurrences |
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multiplicity |
the range of occurrences of an entity per instance of a related entity |
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Define: Derived attribute |
attribute that represents a value that is derivable from value of a related attribute, or set of attributes, not necessarily in the same entity type |
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Example: Derived attribute |
Age derived from DOB and Today's date |
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