SQL & PL/SQL

Would someone please tell me where is my mistake here...

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SET SERVEROUTPUT ON
DECLARE
TYPE dept_table_type IS TABLE OF
departments%ROWTYPE INDEX BY PLS_INTEGER;
my_dept_table dept_table_type;
max_count NUMBER(4,0):= 30;
BEGIN
FOR i IN 10..max_count
LOOP
SELECT * INTO my_dept_table(i) FROM departments
WHERE department_id = i;
END LOOP;
FOR i IN my_dept_table.FIRST..my_dept_table.LAST
LOOP
DBMS_OUTPUT.PUT_LINE(my_dept_table(i).department_name);
END LOOP;
END;
/
=====================================

I am getting the error...
===============
Error report:
ORA-01403: no data found
ORA-06512: at line 9
01403. 00000 - "no data found"
*Cause:
*Action:
===============


Thanks for your help!