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Relationships. “ S ituation that exists between two relational database tables ”. It stop the need for repeating data A llows the database to be smaller in size Makes it easier to update, add and delete information It also makes searching the database easier. Data Redundancy.

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Presentation Transcript
s ituation that exists between two relational database tables
“Situation that exists between two relational database tables”
  • It stop the need for repeating data
  • Allows the database to be smaller in size
  • Makes it easier to update, add and delete information
  • It also makes searching the database easier
data redundancy
Data Redundancy

This is a flat file database, boo hiss!!!

The problem is that we have redundancy

how to solve the issue
How to solve the issue
  • Simply take the data out
  • Make another table

Students

Teachers

different types of relationship
Different types of relationship

Table 1

Table 2

  • One to One
    • A persons credit check
  • One to Many
    • A teacher and students
  • Many to Many
    • Online orders

Table 1

Table 2

Table 1

Table 2

Important Fact

This can never be made, as the database wont allow it

the task
The Task
  • You need to design a second table in your ERD for actors
  • Then you need to build the table
  • Add some actors into your table and link them with films.

Extension Challenge

Try and find the problem with using a 1 to many relationship

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