Convert rows to columns in sql database

Question

Hi Team,
I have a table called as ABC in test schema which have got 3 columns
      ABC
COL1   VARCHAR2(10)
COL2    VARCHAR2(10)
COL3    VARCHAR2(10)
The dat in ABC table is as follows
           ABC
COL1           COL2            COL3
A                   B                  C
I wanted to write a sql query which will give me
COL
A
B
C
Appreciate your help on the above?
Thanks & Regards,
Thakur Manoj R

Answer 1

Gurjeet wrote:
with t as ( select deptno ||',' || dname || ',' || loc  as abc from dept where deptno =10)
  select regexp_substr(abc,'[^,]+', 1, level) from t
   connect by regexp_substr(abc, '[^,]+', 1, level) is not null
That is a completely wrong answer.
The OP was not asking how to split a comma seperated string, he was asking how to unpivot individual columns to a single column.
That can be achieved using the UNPIVOT functionality in SQL, if the database version supports it, or if not something as simple as:
SQL> ed
Wrote file afiedt.buf
  1  with t as (select 'A' as col1, 'B' as col2, 'C' as col3 from dual union all
  2             select 'X','Y','Z' from dual)
  3  --
  4  -- end of test data
  5  --
  6  select decode(rn,1,col1,2,col2,col3) as col
  7  from   t
  8*        cross join (select rownum rn from dual connect by rownum <= 3)
SQL> /
C
A
X
B
Y
C
Z
6 rows selected.