Identify columns after fetching cursor

Question

Hi,
I have a scenario in which iam reading the columns into a cursor and during fetch I want to apply some condition against each column in the cursor.
Eg:
curcor c1 is Select col1,col2,col3 from test;
rec1 c1%rowtype;
begin
open c1;
loop
fetch c1 into rec1;
exit when c1%NOTFOUND;
if rec1.col1=1234
Here instead of using column name can I know that this is the first column in the cursor and apply multiple validations and similarly to next column and so on.
Regards
Satya

Answer 1

If you want to reference columns by position then you either need to be using a ref cursor via a 3rd party developement language like .NET etc. or you need to use the DBMS_SQL package within PL/SQL.
Example of using DBMS_SQL package (from my standard library of examples - in this case something that takes a query and outputs the data as CSV)...
As sys user:
CREATE OR REPLACE DIRECTORY TEST_DIR AS '\tmp\myfiles'
GRANT READ, WRITE ON DIRECTORY TEST_DIR TO myuser
/As myuser:
CREATE OR REPLACE PROCEDURE run_query(p_sql IN VARCHAR2
                                     ,p_dir IN VARCHAR2
                                     ,p_header_file IN VARCHAR2
                                     ,p_data_file IN VARCHAR2 := NULL) IS
  v_finaltxt  VARCHAR2(4000);
  v_v_val     VARCHAR2(4000);
  v_n_val     NUMBER;
  v_d_val     DATE;
  v_ret       NUMBER;
  c           NUMBER;
  d           NUMBER;
  col_cnt     INTEGER;
  f           BOOLEAN;
  rec_tab     DBMS_SQL.DESC_TAB;
  col_num     NUMBER;
  v_fh        UTL_FILE.FILE_TYPE;
  v_samefile  BOOLEAN := (NVL(p_data_file,p_header_file) = p_header_file);
BEGIN
  c := DBMS_SQL.OPEN_CURSOR;
  DBMS_SQL.PARSE(c, p_sql, DBMS_SQL.NATIVE);
  d := DBMS_SQL.EXECUTE(c);
  DBMS_SQL.DESCRIBE_COLUMNS(c, col_cnt, rec_tab);
  FOR j in 1..col_cnt
  LOOP
    CASE rec_tab(j).col_type
      WHEN 1 THEN DBMS_SQL.DEFINE_COLUMN(c,j,v_v_val,2000);
      WHEN 2 THEN DBMS_SQL.DEFINE_COLUMN(c,j,v_n_val);
      WHEN 12 THEN DBMS_SQL.DEFINE_COLUMN(c,j,v_d_val);
    ELSE
      DBMS_SQL.DEFINE_COLUMN(c,j,v_v_val,2000);
    END CASE;
  END LOOP;
  -- This part outputs the HEADER
  v_fh := UTL_FILE.FOPEN(upper(p_dir),p_header_file,'w',32767);
  FOR j in 1..col_cnt
  LOOP
    v_finaltxt := ltrim(v_finaltxt||','||lower(rec_tab(j).col_name),',');
  END LOOP;
  --  DBMS_OUTPUT.PUT_LINE(v_finaltxt);
  UTL_FILE.PUT_LINE(v_fh, v_finaltxt);
  IF NOT v_samefile THEN
    UTL_FILE.FCLOSE(v_fh);
  END IF;
  -- This part outputs the DATA
  IF NOT v_samefile THEN
    v_fh := UTL_FILE.FOPEN(upper(p_dir),p_data_file,'w',32767);
  END IF;
  LOOP
    v_ret := DBMS_SQL.FETCH_ROWS(c);
    EXIT WHEN v_ret = 0;
    v_finaltxt := NULL;
    FOR j in 1..col_cnt
    LOOP
      CASE rec_tab(j).col_type
        WHEN 1 THEN DBMS_SQL.COLUMN_VALUE(c,j,v_v_val);
                    v_finaltxt := ltrim(v_finaltxt||',"'||v_v_val||'"',',');
        WHEN 2 THEN DBMS_SQL.COLUMN_VALUE(c,j,v_n_val);
                    v_finaltxt := ltrim(v_finaltxt||','||v_n_val,',');
        WHEN 12 THEN DBMS_SQL.COLUMN_VALUE(c,j,v_d_val);
                    v_finaltxt := ltrim(v_finaltxt||','||to_char(v_d_val,'DD/MM/YYYY HH24:MI:SS'),',');
      ELSE
        DBMS_SQL.COLUMN_VALUE(c,j,v_v_val);
        v_finaltxt := ltrim(v_finaltxt||',"'||v_v_val||'"',',');
      END CASE;
    END LOOP;
  --  DBMS_OUTPUT.PUT_LINE(v_finaltxt);
    UTL_FILE.PUT_LINE(v_fh, v_finaltxt);
  END LOOP;
  UTL_FILE.FCLOSE(v_fh);
  DBMS_SQL.CLOSE_CURSOR(c);
END;This allows for the header row and the data to be written to seperate files if required.
e.g.
SQL> exec run_query('select * from emp','TEST_DIR','output.txt');
PL/SQL procedure successfully completed.Output.txt file contains:
empno,ename,job,mgr,hiredate,sal,comm,deptno
7369,"SMITH","CLERK",7902,17/12/1980 00:00:00,800,,20
7499,"ALLEN","SALESMAN",7698,20/02/1981 00:00:00,1600,300,30
7521,"WARD","SALESMAN",7698,22/02/1981 00:00:00,1250,500,30
7566,"JONES","MANAGER",7839,02/04/1981 00:00:00,2975,,20
7654,"MARTIN","SALESMAN",7698,28/09/1981 00:00:00,1250,1400,30
7698,"BLAKE","MANAGER",7839,01/05/1981 00:00:00,2850,,30
7782,"CLARK","MANAGER",7839,09/06/1981 00:00:00,2450,,10
7788,"SCOTT","ANALYST",7566,19/04/1987 00:00:00,3000,,20
7839,"KING","PRESIDENT",,17/11/1981 00:00:00,5000,,10
7844,"TURNER","SALESMAN",7698,08/09/1981 00:00:00,1500,0,30
7876,"ADAMS","CLERK",7788,23/05/1987 00:00:00,1100,,20
7900,"JAMES","CLERK",7698,03/12/1981 00:00:00,950,,30
7902,"FORD","ANALYST",7566,03/12/1981 00:00:00,3000,,20
7934,"MILLER","CLERK",7782,23/01/1982 00:00:00,1300,,10The procedure allows for the header and data to go to seperate files if required. Just specifying the "header" filename will put the header and data in the one file.
Adapt to output different datatypes and styles are required.