In reference to comment, I do not know how to post sample data, I am working in a student database we connect to.I ran the subqueries separately and returned values fine, when I put the first part in to try to add it all together, it runs but returns no rows.

I am trying to solve: Find how many students are enrolled in sections taught by Todd Smythe. Can someone help my fix my code? I am having no rows returned.

My code:

SELECT COUNT(STUDENT_ID) FROM ENROLLMENT

WHERE SECTION_ID IN

(SELECT SECTION_ID FROM SECTION

WHERE SECTION_NO IN

(SELECT SECTION_NO FROM SECTION

WHERE SECTION.INSTRUCTOR_ID =

(SELECT INSTRUCTOR_ID FROM INSTRUCTOR

WHERE FIRST_NAME='TODD' AND LAST_NAME='SMYTHE')));

Tables from database

Name Null Type

------------- -------- ------------ENROLLMENT TABLE

STUDENT_ID NOT NULL NUMBER(8)

SECTION_ID NOT NULL NUMBER(8)

ENROLL_DATE NOT NULL DATE

FINAL_GRADE NUMBER(3)

CREATED_BY NOT NULL VARCHAR2(30)

CREATED_DATE NOT NULL DATE

MODIFIED_BY NOT NULL VARCHAR2(30)

MODIFIED_DATE NOT NULL DATE

Name Null Type

--------------- -------- ------------SECTION TABLE

SECTION_ID NOT NULL NUMBER(8)

COURSE_NO NOT NULL NUMBER(8)

SECTION_NO NOT NULL NUMBER(3)

START_DATE_TIME DATE

LOCATION VARCHAR2(50)

INSTRUCTOR_ID NOT NULL NUMBER(8)

CAPACITY NUMBER(3)

CREATED_BY NOT NULL VARCHAR2(30)

CREATED_DATE NOT NULL DATE

MODIFIED_BY NOT NULL VARCHAR2(30)

MODIFIED_DATE NOT NULL DATE

Name Null Type

------------- -------- ------------COURSE TABLE

COURSE_NO NOT NULL NUMBER(8)

DESCRIPTION NOT NULL VARCHAR2(50)

COST NUMBER(9,2)

PREREQUISITE NUMBER(8)

CREATED_BY NOT NULL VARCHAR2(30)

CREATED_DATE NOT NULL DATE

MODIFIED_BY NOT NULL VARCHAR2(30)

Name Null Type

-------------- -------- ------------Instructor table

INSTRUCTOR_ID NOT NULL NUMBER(8)

SALUTATION VARCHAR2(5)

FIRST_NAME VARCHAR2(25)

LAST_NAME VARCHAR2(25)

STREET_ADDRESS VARCHAR2(50)

ZIP VARCHAR2(5)

PHONE VARCHAR2(15)

CREATED_BY NOT NULL VARCHAR2(30)

CREATED_DATE NOT NULL DATE

MODIFIED_BY NOT NULL VARCHAR2(30)

MODIFIED_DATE NOT NULL DATE

Name Null Type

----------------- -------- ------------STUDENT TABLE

STUDENT_ID NOT NULL NUMBER(8)

SALUTATION VARCHAR2(5)

FIRST_NAME VARCHAR2(25)

LAST_NAME NOT NULL VARCHAR2(25)

STREET_ADDRESS VARCHAR2(50)

ZIP NOT NULL VARCHAR2(5)

PHONE VARCHAR2(15)

EMPLOYER VARCHAR2(50)

REGISTRATION_DATE NOT NULL DATE

CREATED_BY NOT NULL VARCHAR2(30)

CREATED_DATE NOT NULL DATE

MODIFIED_BY NOT NULL VARCHAR2(30)

MODIFIED_DATE NOT NULL DATE