Dynamic Column Name for a Derived Column - ORACLE SQL

Question

I'm trying to set a dynamic column name on my query using "select from dual". Is this possible? If not, kindly recommend alternatives for me to achieve this. I need this on a normal select query, not by using a stored procedure.

I'm trying to achieve the query below:

SELECT  A.NO
        ,A.SUB_NO
        ,A.DCY
        ,A.STATE

        ,NVL(TO_CHAR(M1.NUMERATOR),'0') AUG_NUM     --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-2),'MON')||'_NUM' FROM DUAL
        ,NVL(TO_CHAR(M1.DENOMINATOR),'0') AUG_DEN   --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-2),'MON')||'_DEN' FROM DUAL

        ,NVL(TO_CHAR(M2.NUMERATOR),'0') JUL_NUM     --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-3),'MON')||'_NUM' FROM DUAL
        ,NVL(TO_CHAR(M2.DENOMINATOR),'0') JUL_DEN   --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-3),'MON')||'_DEN' FROM DUAL

        ,NVL(TO_CHAR(M3.NUMERATOR),'0') JUN_NUM     --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-4),'MON')||'_NUM' FROM DUAL
        ,NVL(TO_CHAR(M3.DENOMINATOR),'0') JUN_DEN   --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-4),'MON')||'_DEN' FROM DUAL

        ,M1.M1_CALC
        ,M2.M2_CALC
        ,M3.M3_CALC

FROM A, M1,M2,M3;

Thank you in advance for your help.

Answer 1

I'm pretty sure the closest you're going to get to what you want is by using a UNION ALL .

SELECT NULL no,
       NULL sub_no,
       NULL dcy,
       NULL state,
       TO_CHAR(ADD_MONTHS(SYSDATE,-2),'MON')||'_NUM' AUG_NUM,
       TO_CHAR(ADD_MONTHS(SYSDATE,-2),'MON')||'_DEN' AUG_DEN,
       TO_CHAR(ADD_MONTHS(SYSDATE,-3),'MON')||'_NUM' JUL_NUM,
       TO_CHAR(ADD_MONTHS(SYSDATE,-3),'MON')||'_DEN' JUL_DEN,
       TO_CHAR(ADD_MONTHS(SYSDATE,-4),'MON')||'_NUM' JUN_NUM,
       TO_CHAR(ADD_MONTHS(SYSDATE,-4),'MON')||'_DEN' JUN_DEN,
       NULL M1_CAL,
       NULL M2_CALC,
       NULL M3_CALC
FROM dual
UNION ALL
SELECT  A.NO
        ,A.SUB_NO
        ,A.DCY
        ,A.STATE

        ,NVL(TO_CHAR(M1.NUMERATOR),'0') AUG_NUM     --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-2),'MON')||'_NUM' FROM DUAL
        ,NVL(TO_CHAR(M1.DENOMINATOR),'0') AUG_DEN   --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-2),'MON')||'_DEN' FROM DUAL

        ,NVL(TO_CHAR(M2.NUMERATOR),'0') JUL_NUM     --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-3),'MON')||'_NUM' FROM DUAL
        ,NVL(TO_CHAR(M2.DENOMINATOR),'0') JUL_DEN   --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-3),'MON')||'_DEN' FROM DUAL

        ,NVL(TO_CHAR(M3.NUMERATOR),'0') JUN_NUM     --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-4),'MON')||'_NUM' FROM DUAL
        ,NVL(TO_CHAR(M3.DENOMINATOR),'0') JUN_DEN   --AS SELECT TO_CHAR(ADD_MONTHS(SYSDATE,-4),'MON')||'_DEN' FROM DUAL

        ,M1.M1_CALC
        ,M2.M2_CALC
        ,M3.M3_CALC
FROM A, M1,M2,M3;