How can I dynamically recover columnName_N from a cursor, N being a number incremented in a LOOP?

Question

thanks for taking time to read and maybe answer my question! Note that I am a beginner and should not be considered a pro but i did search for the answer without finding it , maybe due to my uncommon problem and/or lack of knowledge about it.

I have the following problem at work, i know it is not really supposed to happen, but here it is, on my desk... :

I have a table (conv_temp1) with the following columns:

ID No Sigle Info COLUMN_1 COLUMN_2 COLUMN_3 COLUMN_4 COLUMN_5 .. COLUMN_50

I have this cursor:

 CURSOR c_minis IS
        SELECT *
        FROM conv_temp1;

I am trying to do something as the following:

FOR v_rsrec IN c_minis LOOP
   l_column_i := 1;
   dbms_output.put_line('----- Beginning - v_rsrec.id ----');
     FOR boucle IN REVERSE 1.. 50 LOOP

       --this is my problem, i am trying to acces a cursor column "dynamically"
       EXECUTE IMMEDIATE 'v_declared_varchar2 := COLUMN_'|| l_column_i ||';';  

       IF v_declared_varchar2 IS NOT NULL THEN
         dbms_output.put_line('I am doing something with the information!');
         --(Dont worry, YES I am re-structuring it in a new table...)


       END IF;
       l_column_i := l_column_i + 1;
     END LOOP;
   dbms_output.put_line('-----c end - v_rsrec.id ----');
END LOOP;

Is there a way to perform such a thing as accessing a different column (only the number changes in the name of those) depending on where i am in my iterations? ex, if I have already done 10 iterations, i will recover information from COLUMN_11 in my cursor.

Answer 1

A better solution would be to normalize the table. Break it into two tables as:

CREATE TABLE CONV_TEMP_HEADER
  (ID_NO        NUMBER
     CONSTRAINT PK_CONV_TEMP_HEADER
       PRIMARY KEY
       USING INDEX,
   SIGLE_INFO   VARCHAR2(100));  -- or whatever

CREATE TABLE CONV_TEMP_DETAIL
  (ID_DETAIL    NUMBER,
   ID_NO        NUMBER
     CONSTRAINT CONV_TEMP_DETAIL_FK1
       REFERENCES CONV_TEMP_HEADER(ID_NO)
         ON DELETE CASCADE,
   IDX          NUMBER,
   COLUMN_VALUE VARCHAR2(100)
   CONSTRAINT CONV_TEMP_DETAIL_UQ1
     UNIQUE(ID_NO, IDX));

This way, instead of having to generate column names dynamically and figure out how to use DBMS_SQL, you can get your data using a simple join:

SELECT h.*, d.*
  FROM CONV_TEMP_HEADER h
  LEFT OUTER JOIN CONV_TEMP_DETAIL d
    ON d.ID_NO = h.ID_NO;

Share and enjoy.