Whenever you alter the value of a column referenced by the -- All the employees except the manager of -- department (WORKDEPT) 'E21' have been temporarily reassigned.-- Indicate this by changing their job (JOB) to NULL and their pay -- (SALARY, BONUS, COMM) values to zero in the EMPLOYEE table.
Since you can't list more than one table in the Oracle UPDATE statement, you can use the Oracle EXISTS clause.
Second, the SET clause specifies which column that you want to modify and the new values.
A searched update statement depends on the table being updated, all of its conglomerates (units of storage such as heaps or indexes), all of its constraints, and any other table named in the WHERE clause or SET expressions.
A CREATE or DROP INDEX statement or an ALTER TABLE statement for the target table of a prepared searched update statement invalidates the prepared searched update statement.
The Oracle UPDATE statement is used to update existing records in a table in an Oracle database.