FORALL Concept In PL SQL

CREATE TABLE emp_by_dept AS
SELECT employee_id, department_id FROM employees WHERE 1 = 0;

DECLARE
TYPE dept_tab
IS
TABLE OF departments.department_id%TYPE;
deptnums dept_tab;
TYPE NumList
IS
TABLE OF NUMBER;
-- The zeros in this list will cause divide-by-zero errors.
num_tab NumList := NumList(10,0,11,12,30,0,20,199,2,0,9,1);
errors NUMBER;
dml_errors EXCEPTION;
PRAGMA exception_init(dml_errors, -24381);
BEGIN
SELECT
department_id BULK COLLECT
INTO
deptnums
FROM
departments;
-- SAVE EXCEPTIONS means don't stop if some INSERT fail.
FORALL i IN 1..deptnums.COUNT SAVE EXCEPTIONS
INSERT
INTO
emp_by_dept
SELECT
employee_id,
department_id
FROM
employees
WHERE
department_id = deptnums(i);
FOR i IN 1..deptnums.COUNT
LOOP
-- Count how many rows were inserted for each department; that is,
-- how many employees are in each department.
dbms_output.put_line('Dept '||deptnums(i)||': inserted '||
SQL%BULK_ROWCOUNT(i)||' records');
END LOOP;
dbms_output.put_line('Total records inserted =' || SQL%ROWCOUNT);
-- If any errors occurred during the FORALL SAVE EXCEPTIONS,
-- a single exception is raised when the statement completes.
EXCEPTION
WHEN dml_errors THEN -- Now we figure out what failed and why.
errors := SQL%BULK_EXCEPTIONS.COUNT;
dbms_output.put_line('Number of INSERT statements that failed: ' || errors);
FOR i IN 1..errors
LOOP
dbms_output.put_line('Error #' || i || ' occurred during '|| 'iteration #'
|| SQL%BULK_EXCEPTIONS(i).ERROR_INDEX);
dbms_output.put_line('Error message is ' ||
SQLERRM(-SQL%BULK_EXCEPTIONS(i).ERROR_CODE));
END LOOP;
END;