SQL Training - 03

Identity Field:

• Indexed 
• No duplicate 
• Auto Increment 
• sorted
• Indexed 

Side Effect of Identity Field:

• Values cannot be changed 
• Gaps 

Normalization:

• we need it to prevent redundancy (Place are repeated)
• To avoid repeated columns (Address, 2 , 3)
• To avoid repeated rows 
• Referential integrity (Relations to make full record)
• Unity: each table must contains all related data
• Atomic: each cell must be one value 
• Dependency
• To prevent orphan rows (customer without address or addresses without customers)
• No Transitive 

- Use begin transaction and end transaction to execute more-than one sql statement 

- In One to many relations; you add in many table and after that you add in one table.

- In Addresses table; you can add email1, email2, phone1, phone2, telephone1, telephone2, fax1, fax2

SW Engineering:

• Gathering info
• Structured 
• OO
• Noun: classes
• Verbs: functions
• Each property in class is a field in DB
• Structred
• Verbs only 
• UML classes
• Class contains 
• Class Members
• Properties (Name, Age)
• Methods  (Add, Delete)
• Events(WhenDeleted, WhenAdded)

PrimMinister, Manager, Employee, Driver, Heads of Units, Drivers, Cleaners are Persons 

so the initial table is Person,