Relationships
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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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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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