• Sometimes we need to provide some restriction on the data for security and data integrity reason.
  • We must ensure that only valid and complete data should be stored into the database.
  • Oracle allows data integrity constraints to ensure data consistency and data integrity.
  • They are known as integrity constrains.
  • Oracle supports two type of integrity constrains:
  1. I/O Constraints

  2. Business Constraints

  • Constraints that control data insertion and data retrieval speed are known as I/O constraints.
  • Business constraints are the constraints defined by the organization itself.
  • They define business rules or policy.
  • Constraints can be defined either at the time of table creation by using CREATE TABLE command or can be define on existing table by using ALTER TABLE command.
  • It can be define either at table level or at column level.

Table level Constraints:

  • Constraints that span across multiple columns are known as table level constraints.
  • Table level constraints are defined after the table definition with CREATE TABLE command.

Column level Constraints:

  • Constraints which are defined on a specific column are known as column level constraints.
  • They are specific to single column.
  • Fore more detail read our articles  on I/O constraints and Business constraints.