What is normalization concept

if a table called Student as below with 4 columns and data as below

Student table

StudentName YearOfStudy Subject TeacherName
john                    10thGrade    Maths    Ashley

why it is better to move away Teacher information to separate table as below

Teacher Table

TeacherName TeachingSubject
Ashley                 Maths

what is various types of normalizations?
Please advise
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Ryan ChongBusiness Systems Analyst , ex-Senior Application EngineerCommented:
why it is better to move away Teacher information to separate table as below
in general speaking, to ease the process of data updating and reduce duplicate of data.
Yes, creating a teacher table that will include much more then just the teacher's name, potentially include contact information, subject matter expertise (separate table since sone teachers might have multiple subject expertise)
With just this change
Teacherid teachername teacheremail
1 Ashley
For this example only changing one item the teacher reference

Studentid student-name grade teacherref_id
1 John 10th 1

What this provides is minimizing storage space while maximizing info.
Michael EspeyoperatorCommented:
If the name of the teachers changes (eg marriage), you only have to change it once.

Besides, if you don't normalize it to the 1st form, you're open to spelling errors.

So, in the same class it can happen that students have Mr Smith and Mr Simth as a teacher.
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John TsioumprisSoftware & Systems EngineerCommented:
Well you small example should be modified like this :
Table Student
StudentID           1
StudentName     John

Table StudyYears
YearID                  1
Year                      10thGrade    

Table Lesson
LessonID               1
Lesson                    Maths

Table Teachers
TeacherID                1
Teacher                     Ashley

Then you could have a :
Table StudentAttendance      
Student                                     1
YearOfStudy                             1
Lesson                                       1
Teacher                                      1  

TeacherID                                 1
LessonID                                   1

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Vitor MontalvãoMSSQL Senior EngineerCommented:
what is various types of normalizations?
There's only one:
Vitor MontalvãoMSSQL Senior EngineerCommented:
All valid inputs.
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