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42 Cards in this Set
- Front
- Back
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Why was file processing as a data system discarded?
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1-Data was hard to get to
2-Data was duplicated 3-Application dependent 4-Couldn't change to newer/different systems(mac-win-unix) |
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A true Database consists of: (4)
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1-integrated data
2-reduced data duplication 3-application independent 4-easy representation of the users reality |
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DBMS contains: (4)
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1-Metadata / data definition / data dictionary
2-index 3-program 4-application metadata such as reports, forms, queries |
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Data Modeling
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Process of creating a logical representation of the structure of the database
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Entity Relationship consists of:(4)
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Entities
Attributes Identifier Relationship |
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What is an entity
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An object that the user wants to track, usually a noun, ie EMPLOYEE
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Entity classes
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Entities of a given type
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Identifier
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Uniquely identifies a row in a table
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relationship
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how entities are related:
one to one one to many many to many |
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Unified Modeling Language
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Set of structures and techniques for modeling that includes information about object constraints and methods.
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Attribute
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Specifies what details are collected for each object.
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Simple Attribute
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a single data element
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Group attribute
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composite of related attributes such a address (no. and street)
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Semantic Object Attribute
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Object link-links back to a class
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Semantic Object Attribute
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Object link-links back to a class
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Top Down Design uses what data model
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E-R Diagram
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Bottom up design uses what model?
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SOM
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What is a domain?
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Set of values that a column may have
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What is Normalization
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The process of eliminating duplicating data.
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Rows contain
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relationships or tuples
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columns contain
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attributes
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1NF
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a relation must have only single-valued attributes
neither repeating groups nor arrays are permitted |
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2NF
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Must be in 1nf and each non key attribute must be dependent on the whole key (might have composite keys)
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3NF
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Must be in 2NF
No transitive dependencies may exist |
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Transitive dependency
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an attribute is dependent on another key, ie total price (qty x price)
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BCNF
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Must be in 3NF
Every determinant must be a candidate key |
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4NF
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Must be a BCNF
May not contain multi-valued dependencies |
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1NF
2NF 3NF BCNF 4NF |
1NF-any relationship
2NF-all nonkey attributes are dependent on the entire key 3NF-no transitive dependencies BCNF-every determinant is a candidate key 4NF |
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What are the 4 common relationship patterns?
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1-tree
2-simple networks 3-complex networks 4-bills of materials |
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Tree relationship - cardinality?
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hierarchy
1:N |
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Simple network - cardinality?
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Only 1 : N
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Complex Network -cardinality
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has at least a N : M relationship
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Bills of Materials - relationship pattern?
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Parent relations are viewed as composites of the child relations--viewed from the bottom up.
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null value
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an attribute that has never been supplied.
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Cardinality-max and min
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indicates the max number of instances involved in a relationship
Min-indicates optional (0) or mandatory (1) relationship |
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Data Integrity
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Stored logically consistent. Not duplicated in multiple tables
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Moor's Law
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Information doubles every 18 months and prices halves during the same time.
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What is business rules?
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Constrictions on business activities that must show up in the Database.
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What is the difference between a class and an instance?
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Class-Naming convention-DEPARTMENT
Instance-an occurance-ehs |
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A surrogate key
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A number or code to give meaning to the information attached (autonumber)
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surrogate key
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ID's that have no real meaning other than to be a unique key
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Attributes
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Describes a characteristic of an entity, ie. employee name, employee ID, color,
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