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Basic Understanding of Referential Integrity

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Referential Integrity

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itse 2347

ITSE 2347

Referential Integrity

referential integrity
Referential Integrity

Referential Integrityis an optional system of rules that guarantees the relationships are valid and the databases will remain intact as data is entered, edited, or deleted.

referential integrity3
Referential Integrity

Basic RulesFor every record in a child table ( the “many” side) one and only one matching record must be in the parent table ( the “one” side).

referential integrity4
Referential Integrity

Example Look at a Parent/Child relationship.

Without a Parent there is no Child.

referential integrity5
Referential Integrity

Example In order to have a work order you would need a customer that would be receiving the work.

The Customer would be the Parent.

The Work order would be the Child.

referential integrity6
Referential Integrity

Before you can set referential integrity the following conditions must be met.

referential integrity conditions
Referential Integrity/ Conditions
  • The matching field in the parent table is the primary key or has a unique value.
  • Related Field are the same data type.
  • Both tables are in the same Database.
referential integrity conditions8
Referential Integrity/ Conditions
  • Every record has one and only one matching record in the table.
tables can be joined in three ways
Tables can be joined in three ways
  • One-to-One
  • One-to-Many
  • Many-to-Many
a one to many relationship
A one-to-many relationship

A one-to-many relationship exists when one table has many records associated with a given value but the related table has only one record for that value.

  • The table with one record is called the primary table
  • The table with many records is called the related table
a one to many relationship12
A one-to-many relationship

One Employer------Many Positions

a one to many relationship13
A one-to-many relationship

We can’t remove the Employer table because it would delete all of the employers from the Position table.