Database Processing
Terms
undefined, object
copy deck
- 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) - 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 - 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 - Data Modeling
- Process of creating a logical representation of the structure of the database
- Entity Relationship consists of:(4)
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Entities
Attributes
Identifier
Relationship - What is an entity
- An object that the user wants to track, usually a noun, ie EMPLOYEE
- Entity classes
- Entities of a given type
- Identifier
- Uniquely identifies a row in a table
- relationship
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how entities are related:
one to one
one to many
many to many - Unified Modeling Language
- Set of structures and techniques for modeling that includes information about object constraints and methods.
- Attribute
- Specifies what details are collected for each object.
- Simple Attribute
- a single data element
- Group attribute
- composite of related attributes such a address (no. and street)
- Semantic Object Attribute
- Object link-links back to a class
- Top Down Design uses what data model
- E-R Diagram
- Bottom up design uses what model?
- SOM
- What is a domain?
- Set of values that a column may have
- What is Normalization
- The process of eliminating duplicating data.
- Rows contain
- relationships or tuples
- columns contain
- attributes
- 1NF
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a relation must have only single-valued attributes
neither repeating groups nor arrays are permitted - 2NF
- Must be in 1nf and each non key attribute must be dependent on the whole key (might have composite keys)
- 3NF
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Must be in 2NF
No transitive dependencies may exist - Transitive dependency
- an attribute is dependent on another key, ie total price (qty x price)
- BCNF
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Must be in 3NF
Every determinant must be a candidate key - 4NF
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Must be a BCNF
May not contain multi-valued dependencies -
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 - What are the 4 common relationship patterns?
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1-tree
2-simple networks
3-complex networks
4-bills of materials - Tree relationship - cardinality?
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hierarchy
1:N - Simple network - cardinality?
- Only 1 : N
- Complex Network -cardinality
- has at least a N : M relationship
- Bills of Materials - relationship pattern?
- Parent relations are viewed as composites of the child relations--viewed from the bottom up.
- null value
- an attribute that has never been supplied.
- 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 - Data Integrity
- Stored logically consistent. Not duplicated in multiple tables
- Moor's Law
- Information doubles every 18 months and prices halves during the same time.
- What is business rules?
- Constrictions on business activities that must show up in the Database.
- What is the difference between a class and an instance?
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Class-Naming convention-DEPARTMENT
Instance-an occurance-ehs - A surrogate key
- A number or code to give meaning to the information attached (autonumber)
- surrogate key
- ID's that have no real meaning other than to be a unique key
- Attributes
- Describes a characteristic of an entity, ie. employee name, employee ID, color,