Altering a Trigger Header
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When used to change only a trigger header, ALTER TRIGGER requires at least one altered setting after the trigger name. Any setting omitted from ALTER TRIGGER remains unchanged.
The following statement makes the trigger, SAVE_SALARY_CHANGE, inactive:
ALTER TRIGGER SAVE_SALARY_CHANGE INACTIVE;
If the time indicator (BEFORE or AFTER) is altered, then the operation (UPDATE, INSERT, or DELETE) must also be specified. For example, the following statement reactivates the trigger, VERIFY_FUNDS, and specifies that it fire before an UPDATE instead of after:
ALTER TRIGGER SAVE_SALARY_CHANGE
ACTIVE
BEFORE UPDATE;