Facing error 'No data found ' while trying to write a query using 'Cursor' PL/SQL in oracle

Question

Hope you're doing well. I'm new to oracle PL/SQL and I'm trying to write a query just with the aim of practicing 'Cursor's . I have three tables with below structures :

Student:(Student_id , Student_name)
Course :(COURSE_NO , description)
Student_Course:(Student_id , Course_id , Nomreh)

Table Student_Course stores each student's mark in each course . the word 'Nomreh' is the Persian of Mark. I just want to know what wrong with my query is? Everything seems flawless! But I receive these errors :

ORA-01403:no data found
ORA-06512:at line 13

Here is my query :

DECLARE
  CURSOR C1 IS
        SELECT S.STUDENT_ID FROM STUDENT S;

        C1_REC               C1%ROWTYPE;
        V_STUDENT_FIRST_NAME STUDENT.STUDENT_NAME%TYPE;
        V_COURSE_DESCRIPTION COURSE.DESCRIPTION%TYPE;
        V_NOMRE              STUDENT_COURSE.NOMREH%TYPE;

  BEGIN
     FOR C1_REC IN C1 LOOP

        SELECT S.STUDENT_NAME, C.DESCRIPTION, SC.NOMREH
        INTO V_STUDENT_FIRST_NAME, V_COURSE_DESCRIPTION, V_NOMRE
        FROM STUDENT S
             INNER JOIN STUDENT_COURSE SC
        ON S.STUDENT_ID = SC.STUDENT_ID
             INNER JOIN COURSE C
        ON SC.COURSE_ID = C.COURSE_NO
        WHERE S.STUDENT_ID = C1_REC.STUDENT_ID;

  INSERT INTO TARGETTABLE
  (STUDENT_NAME, COURSE_NAME, NOMRE)
      VALUES
  (V_STUDENT_FIRST_NAME, V_COURSE_DESCRIPTION, V_NOMRE);
 END LOOP;
   COMMIT;
 END;

Thanks in advance

Answer 1

The SQL statement inside the loop may be fine, but it still does not return data.

SELECT ... INTO ... throws an error ORA-01403 when "no data found":

declare
  l_num number;
begin
  select 1 into l_num from dual where 1 = 2;
end;
/

ERROR at line 1:
ORA-01403: no data found
ORA-06512: at line 4

That code you wrote fails no only when the query does not return rows, it would also fail if the query returned multiple rows (a student attending multiple courses):

declare
  l_num number;
begin
  select 1 into l_num from dual connect by level <= 2;
end;
/

ERROR at line 1:
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at line 4

Here is something that should work (just for the sake of this example):

DECLARE
  CURSOR C1 IS
        SELECT S.STUDENT_ID FROM STUDENT S;
        C1_REC               C1%ROWTYPE;
BEGIN
    FOR C1_REC IN C1 LOOP

       INSERT INTO TARGETTABLE
       (STUDENT_NAME, COURSE_NAME, NOMRE)
       SELECT S.STUDENT_NAME, C.DESCRIPTION, SC.NOMREH
       FROM STUDENT S
            INNER JOIN STUDENT_COURSE SC
       ON S.STUDENT_ID = SC.STUDENT_ID
            INNER JOIN COURSE C
       ON SC.COURSE_ID = C.COURSE_NO
       WHERE S.STUDENT_ID = C1_REC.STUDENT_ID;
END LOOP;
  COMMIT;
END; 
/