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9B Data Design (Entity-Relationship
Diagram (ERD) (is a graphic…
9B Data Design
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Data Normalization
Is the process by which we efficiently organize data to achieve these goals:
- Eliminate redundancy
- Eliminate need for restructuring database when data is added
- Ensure data is stored in the correct table
First Normal Form (1NF)
- There are no repeating groups (parent-child record)
- Each record is unique (or unique combination)
- Each cell contain only a single value
Second Normal Form (2NF)
- All non-key fields depend on all components of the primary key
- 1NF with single primary key is auto 2NF
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Data storage & access
involve strategic business tools:
- data warehouse: store data in easily accessible form
- data mining: look for meaningful relationship among data
- data mart
Logical storage: data that user can view, understand and access, regardless of how or where that info is stored (File)
- Consist of characters, a set of related character form a field (data element or data item)
- Logical record is a set of field value
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Codes
Overview
- Save storage space and cost
- Reduce data transmission time and decrease data entry time
- Reduce data input error
Type
- Sequence code: employee no.222 was hired after no.111
- Block sequence code: 1xx for freshman level, 2xx for sophomore
- Alphabetic code: NY for New York
- Significant digit code: postal code
- Derivation code: magazine subscription code
- Cipher code: GRAND indicate price is 562.90$
- Action code: D to display, X to exit
Database Design steps
- Create an initial ERD
- Create an ERD
- Review all the data element
- Review the 3NF designs for all tables
- Double check all data dictionary entries
After creating your final ERD and normalize table design, you can transform them into a database
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