Oracle integrity constraints | Integrity Constraint - oracle tutorial - sql tutorial




What is Oracle Integrity Constraints ?

  • Integrity Constraints are used to prevent entry of invalid information into tables.
 data integrity constraint
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There are five Integrity Constraints Available in Oracle. They are :

  • Integrity Constraints are used to prevent entry of invalid information into tables.
    • Not Null
    • Primary Key
    • Foreign Key
    • Check
    • Unique

Not Null:

  • A column in a table can be specified not null.
  • It's not possible to insert a null in such a column.
  • The default is null.

Primary Key:

  • Primary Key Constraint defines a column or combination of columns which uniquely identifies each row in the table.
  • After creating a primary key, it can be referenced by a foreign key

Foreign Key:

  • This constraint identifies any column referencing the PRIMARY KEY in another table.
  • It establishes a relationship between two columns in the same table or between different tables.
  • One or more columns can be defined as Foreign key.

Unique Key:

  • Unique Key Constraint ensures that a column or a group of columns in each row have a distinct value.
  • A column(s) can have a null value but the values cannot be duplicated

Check Key:

  • Check Key Constraint defines a business rule on a column.
  • All the rows must satisfy this rule.
  • The constraint can be applied for a single column or a group of columns.

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