Oracle Integrity Constraints

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11 years ago

Table of Contents

Overview

Oracle Integrity constraints are set to Oracle database tables and columns. There are several constraints that we can apply to set conditions or to limit the range of values for database objects.

Types of constraints

Some of the constraints are as follows:

NOT NULL
UNIQUE
PRIMARY KEY
FOREIGN KEY
CHECK
ON DELETE CASCADE

NOT NULL

NOT NULL constraint – The database table column must always be filled with a value.

UNIQUE

UNIQUE constraint – The database table column or combination of columns should be is unique.

PRIMARY KEY

PRIMARY KEY constraint – To indicate that the database table column or combination of columns is the primary key for the table.

FOREIGN KEY

FOREIGN KEY constraint – database table column or column combination must exist as a key in a separate database table.

CHECK

CHECK constraint – Boolean expression is true

ON DELETE CASCADE

ON DELETE CASCADE constraint – Deleting a data row leads to the cascading deletion of the data rows in another database table connected via the FOREIGN KEY constraint.

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