Requirements Analysis
Distinguish between words and terms
Word + Word = Term
Employee = a unit with meaning, the smallest indivisible unit = Word
Employee number = Employee + Number, a unit that can be split = Term
Build a word dictionary (fill in only with the divided "words")
* amount vs price
Data Model
Data is formed of entities, attributes, and relationships
relation: an entity in the real world; table: the smallest unit in relational data for separating and storing information
Each entity is composed of attributes and tuples
Attribute (attribute, column, vertical)
Tuple (tuple, row, horizontal)
* tuple = an ordered enumeration of a finite number of things, a set of elements, a record.
Entity -- Relationship (in verb form) -- Entity
Data Modeling
Collect data on information requirements from the user
-> Analyze the discussed requirements
: Conceptual Data Modeling : Extract entity, attribute, and relationship information for the requirements through the analysis process
-> Prepare a standard word and term dictionary
: Logical Data Modeling : Define the attributes between the core entities previously defined and the surrounding entities, and normalize them
-> Prepare a data dictionary
: Physical Data Modeling : Based on the logical data model
Schema (data structure): considering the DBMS characteristics and implementation environment (derived by standards and rules)
Define the data type and size of each column
-> Write a table specification and express it as an ERD
-> Putting the contents expressed in the ERD into the DBMS data tables is the schema
ERD (Data Modeling Diagram) Example:
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The Three Stages of Data Design
Con - Conceptual Design : the stage of drawing the relationships between entities with lines to create an ERD
Log - Logical Design : the stage of finding the 'attributes', going through processes of 'constraints' and 'normalization' = design is completed
Phy - Physical Design : data types and sizes, applying denormalization
