Inserting updating deleting trigger events
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Like a stored procedure, a trigger is a named PL/SQL unit that is stored in the database and can be invoked repeatedly.
Unlike a stored procedure, you can enable and disable a trigger, but you cannot explicitly invoke it.
While a trigger is , which determines whether the trigger fires before or after the triggering statement runs and whether it fires for each row that the triggering statement affects. If the trigger is created on a schema or the database, then the triggering event is composed of either DDL or database operation statements, and the trigger is called a )".
CREATE or REPLACE TRIGGER emp_after_update AFTER UPDATE OF empid ON emp FOR EACH ROW DECLARE BEGIN update emp_backup set empid = :new.empid where empid = :old.empid; DBMS_OUTPUT.
PUT_LINE('empid successfully updated into emp_backup table'); END; The above trigger named ’emp_after_update’ will be initiated whenever ’empid’ column in ’emp’ table gets updated.
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CREATE or REPLACE TRIGGER emp_after_insert AFTER INSERT ON emp FOR EACH ROW DECLARE BEGIN insert into emp_backup values (:new.empid, :new.fname, :new.lname); DBMS_OUTPUT.
Constraint behavior depends on constraint state, as explained in .
Constraints are easier to write and less error-prone than triggers that enforce the same rules.
In particular, if an uncommitted transaction has modified values that a trigger being fired either must read (query) or write (update), then the SQL statements in the body of the trigger being fired use the following guidelines: privilege.
If this privilege is later revoked, you can drop the trigger but not alter it.
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0) DECLARE sal_diff number; BEGIN sal_diff := : NEW. SAL; dbms_output.put('Old salary: ' || : OLD.sal); dbms_output.put(' New salary: ' || : NEW.sal); dbms_output.put_line(' Difference ' || sal_diff); END; / keyword if you want the trigger to query or change the same table, because triggers can only do that after the initial changes are applied and the table is back in a consistent state.