ALTER ASSERTION

Purpose

Use ALTER ASSERTION to change the properties of an assertion, one of ENABLE, DISABLE, VALIDATE, NOVALIDATE.

Prerequisites

You must have the ALTER ANY ASSERTION [ ON SCHEMA ...] privilege to alter assertions in the specified schema or in any schema not your own.

Syntax

Description of the illustration alter_assertion.gif

Semantics

IF EXISTS

Specify IF EXISTS to prevent an error message in case the assertion you are trying to alter, doesn’t exist.

You cannot use IF NOT EXISTS with ALTER statements.

The following rules apply when you change the property of an assertion:

• Moving from DISABLE to ENABLE, by default, uses VALIDATE. Moving from ENABLE to DISABLE uses NOVALIDATE by default. DISABLE VALIDATE is unsupported.

• Moving between VALIDATE and NOVALIDATE, by default, leaves ENABLE and DISABLE unchanged.

• Moving an assertion from NOVALIDATE to VALIDATE, requires a check of all data. This is potentially an expensive operation.

• Moving an assertion from VALIDATE to NOVALIDATE forgets that the data was ever checked.

• Moving an assertion from ENABLE NOVALIDATE to ENABLE VALIDATE does not block reads, writes, or other DDL. This transition can be done using parallel execution for the validation query.

Examples

Example 1: Disabling an assertion

The following statement disables the assertion company_must_have_a_president:

ALTER ASSERTION IF EXISTS company_must_have_a_president
  DISABLE;

If there is no assertion with this name in the current schema, the statement take no action and completes without error.

Example 3: Validating an assertion

This statement validates the assertion staff_earn_less_than_manager:

ALTER ASSERTION staff_earn_less_than_manager
  VALIDATE;

This runs the assertion on all rows in the query. If existing rows violate the constraint, validation will fail and the statement will raise an error.

Example 3: Enabling an assertion without validation

This statement enables the assertion salary_within_job_limit in the HR schema without checking existing rows comply with it:

ALTER ASSERTION hr.salary_within_job_limit
  ENABLE NOVALIDATE;

If you’re not connected as the HR user, your user must have either of these privileges: ALTER ANY ASSERTION, ALTER ANY ASSERTION ON SCHEMA hr