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| the result of processing raw data to reveal meaning |
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| improved data sharing, data security, integration, minimized data inconsistency, data access, decision making, end-user, productivity |
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| types of data bases - num users, ddatabse location, expected type and extent of use |
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single/multiuser DB
centralized/decentralized
traqnsactional/data warehouse |
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| supportsonly one user at a time |
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| data located in one location |
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| operation(Transaction, Production) |
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| suppports company day to day operations |
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| stores data used for tactical or strategic decisions |
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| why is data base design important? |
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| focuses on design of databases structure for end users |
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| a character or group of characters that has a specific meaning - used to store and define data |
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| logically connected set or more fields |
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3 - must say what to do and how to do it
4 - only have to say what to do |
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| access to a file dependent on its own structure |
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| change file structure without affecting data access |
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| data access changes when data storage characteristics change |
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| data storage characteristics do not affect data access |
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| file system structure makes it difficult to combine data from ____ |
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| organizational structure promotes storage of same data in ____ |
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| different locations - island of info |
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| same data stored unnecessarily in different places |
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| different and conflicting versions of same data occur at different places |
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abnormalities when all changes in redundant data not made correctly
update anomalies
insertion anomalies
deletion anomalies |
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| 5 major pats of data base |
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| hardware, software, people, procedures, data |
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| operating systems, DBMS software, application programs and utility software |
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| data dictionary contains what |
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| data transformation and presentation |
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| DBMS transforms data entered to conform to required data structures |
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| structured query language - de facto |
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| anything about which data is to be collected and stored about |
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| represent detailed description of policies, procedures, or principles within a specific organization |
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| upside down tree...complex to implement, hard to manage, lack structural independence |
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| can have more than one child, records are called owners and members..relationships are called sets |
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| most common, 1970, mathematical concept |
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| an entity occurrence refers to what? |
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| OO data models are depicted using ____ |
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| unified Modeling Language |
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| degrees of data abstraction |
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external - represents end user view
conceptual - global view of db, all external views integrated into single global view
internal - represents view as seen by DBMS |
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| one or more attributes that determine other attributes |
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| a key that consists of 2 or more attributes |
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| attribute B is functionally dependent on A if each value is column A dermines ONE AND ONLY ONE value in column B |
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| an attribute for combination of att that uniquely identifies each row in a table |
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| foreign key must contain values that appear in pk column in related table |
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| all pk are unique, no part of pk my be null |
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| refers to foreign key column which allows us to link tables together |
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defines theoretical way of manipulating table contents using relational operators
ex. select, project, join, intersect, uncion, diff, product, divide |
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| combines all rows form two tables...not duplicate rows |
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| yields only the row that appear in both tables |
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| yields rows in table 1 not found in table 2 |
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| yields all possible pairs of rows from two tables |
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| yields values for all rows found in a table |
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| yields all values for selected attributes |
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| allows info to be combined from 2 or more tabels...natural and outer |
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| used to break up M:M aka bridge |
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| can not be subdivided , gender |
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| value calculated form other att |
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| connectivity vs cardinality |
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connectivity - describes relationship classification
cardinality - expresses min and max number of entity occurrences associated with one occurrence of related entity |
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| entity exists in database only when it is associated with another...dependent is existence dependent on employee |
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| entity can exist apart from one or more related entities |
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| exists if PK of related entity does not contain pk of parent entity |
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| exists when pk of related entity conmtains pk component of parent entity |
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| parent and child graph of entities. has subtype discriminator and partial/overlapping constraints |
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disjoint - can only be one...can be pilot or mechanic not both
overlapping means - could be both |
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| partial vs total completeness |
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partial - some supertype occurrences that are not members of subtypes
total completeness - every supertype occurrence must be member of at least one subtype |
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| top down - identifies more specific entity subtypes from hight level entitiy supertypes |
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| bottom up process - identifies more generic entity supertype form lower level entity subtypes |
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| when should you use composite pk? |
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| weak entities and composite entities |
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| when is a fan trap going to happen? |
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when one entity is in two 1:M relationships
-causes association among other entities not expressed in the model |
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| what does normalization reduce |
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tabl format, no repeating groups
1nf and no partial dependencies
2nf and no transitive dependencies
3nf and no independent multivalues-dependencies |
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| BCNF is special case for? and what does it mean |
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3nf
by definition, a relatino is in BCNF if every determinant in table is a candidate key |
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