Help with query with sub query

Question

hi
I am trying to run the following query and it returns an error as follows:
ORA 00904: ST_ENROLLMENT.absence_reason_code: invalid SQL identfiier.
the code is as follows:
SELECT
        ST_ENROLLMENT.student_id,
        last_name,
        first_name,
        date_of_birth,
        grade_level AS grade,
        gender AS GnDr,
        home_phone_number,
        absence_reason_code
        FROM ST_ENROLLMENT,CE_FAMILY_MEMBER, CE_FAMILY, AT_HOURLY_ATTENDANCE_RECORDS,
       (SELECT
                    COUNT(attendance_status) AS "ConsecutiveDaysAbsent"
                    FROM AT_HOURLY_ATTENDANCE_RECORDS, ST_ENROLLMENT
                 WHERE AT_HOURLY_ATTENDANCE_RECORDS.student_id = ST_ENROLLMENT.student_id
       AND  AT_HOURLY_ATTENDANCE_RECORDS.school_id = ST_ENROLLMENT.school_id
       AND AT_HOURLY_ATTENDANCE_RECORDS.school_year = ST_ENROLLMENT.school_year
       AND ST_ENROLLMENT.district_number = AT_HOURLY_ATTENDANCE_RECORDS.district_number
       AND AT_HOURLY_ATTENDANCE_RECORDS.track_number = ST_ENROLLMENT.track_number
       AND AT_HOURLY_ATTENDANCE_RECORDS.absence_reason_code = ST_ENROLLMENT.absence_reason_code
       AND AT_HOURLY_ATTENDANCE_RECORDS.student_id = ST_ENROLLMENT.student_id); thanks in advance. I appreciate everybody for their help

Answer 1

To avoid a cartesian product, you need to join the tables which are into the from clause. For this, you need to know the column which must be joined.
If I take, for example, some tables from the very know basic schema scott, and I would like the name of emp and the name of dept for each emp, I will join emp table dept table on a common column.
SCOTT@demo102> desc emp
Name                                      Null?    Type
EMPNO                                     NOT NULL NUMBER(4)
ENAME                                              VARCHAR2(10)
JOB                                                VARCHAR2(9)
MGR                                                NUMBER(4)
HIREDATE                                           DATE
SAL                                                NUMBER(7,2)
COMM                                               NUMBER(7,2)
DEPTNO NUMBER(2)
SCOTT@demo102> desc dept
Name                                      Null?    Type
DEPTNO NOT NULL NUMBER(2)
DNAME                                              VARCHAR2(14)
LOC                                                VARCHAR2(13)
SCOTT@demo102> select emp.ename, dept.dname
  2  from emp, dept
  3  where emp.deptno=dept.deptno;
ENAME      DNAME
CLARK      ACCOUNTING
KING       ACCOUNTING
MILLER     ACCOUNTING
JONES      RESEARCH
FORD       RESEARCH
ADAMS      RESEARCH
SMITH      RESEARCH
SCOTT      RESEARCH
WARD       SALES
TURNER     SALES
ALLEN      SALES
ENAME      DNAME
JAMES      SALES
BLAKE      SALES
MARTIN     SALES
14 rows selected.
SCOTT@demo102> HTH,
Nicolas.