CST8215 - Week 3 - CST8215 Week 3 Design concepts The...

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CST8215 Week 3
Design concepts The Design Process Datatypes Normalization
Design process The design process is iterative There is no “perfect” design. Reaching for perfection usually causes more problems. Made up of 4 steps + a end of process review.
Step 1 - Identification Depending on source of data two common paths are available. Path 1 – Recreation/Reverse engineering Path 2 – Clean room implementation Common steps however include: Identify all possible gross data objects. i.e. users, customers, orders, etc. List the objects and categorize them
Step 2 - Describe With each of the objects add all the basic fields. Primary key, descriptor, etc. Try to identify as many fields/properties as possible. Assign datatypes to each of the fields.
Step 3 - Relationships Create connections between objects Identify which objects are parents and which are children Identify which relations are mandatory Create the foreign keys as needed (remember the naming conventions)
Step 4 - Normalization Using the rules of normalization break down the design. The rules are: 1 st NF – tables should have no repeating fields, a primary key and organized in rows 2 nd NF – All data in tables that have correlated PKs must depend on the whole key 3 rd NF – All data must rely on the PK. Create reference tables as needed Replace fields in standard tables with reference table FKs. Goal is to normalize to 3 rd NF.
Step 5 - Review Review the design for potential issues Try to find a peer to review your design After identifying weaknesses, start over at step 1 to implement the changes into the current design. Also review with an eye to the future and try not to over engineer.
Datatypes 1 Text types Char/character – fixed length string, always occupies defined space Varchar/character varying – variable length string, occupies string length + 1 Text – used to large chunks of text MySQL has 3 different types.

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