Help with SQL to Pivot SQL

Question

I have requirment to build the SQL to Merge rows value to a single value.
Here is the Data
TABLE_A
ID SEQ MESG
1 1 MSG1
1 2 MSG2
2 1 MSG1
3 1 MSG1
3 2 MSG2
3 3 MSG3
I need output as
ID MSG
1 MSG1 MSG2
2 MSG1
3 MSG1 MSG2 MSG3

Answer 1

Create function like below:
CREATE OR REPLACE  FUNCTION rowtocol( p_slct IN VARCHAR2, p_dlmtr IN VARCHAR2 DEFAULT ',' ) RETURN VARCHAR2
AUTHID CURRENT_USER AS
    TYPE c_refcur IS REF CURSOR;
    lc_str VARCHAR2(4000);
    lc_colval VARCHAR2(4000);
    c_dummy c_refcur;
    l number;
BEGIN
    OPEN c_dummy FOR p_slct;
    LOOP
    FETCH c_dummy INTO lc_colval;
    EXIT WHEN c_dummy%NOTFOUND;
    lc_str := lc_str || p_dlmtr || lc_colval;
    END LOOP;
    CLOSE c_dummy;
    RETURN SUBSTR(lc_str,2);
       EXCEPTION
       WHEN OTHERS THEN
          lc_str := SQLERRM;
          IF c_dummy%ISOPEN THEN
          CLOSE c_dummy;
          END IF;
       RETURN lc_str;
END;
/And print result like :
   SELECT DISTINCT  a.job,
      rowtocol(  'SELECT ename  FROM emp
                       WHERE
                       job = ' || '''' || a.job || '''' || ' ORDER BY ename'
     AS Employees
    FROM emp;