Oracle 11g unpivot query help

Question

Hello,
I have a single row of data showing school term start and end dates in 2011/12. I need to convert this single row of data (containing 16 columns) into 5 rows comprised of just 4 columns (year, term, term_start, term_end).
Is it possible to use just Oracle 11g's unpivot function_ to convert the following 16 columns of data:
select * from
(select 2012 as terms_year,
1 as T1,'05-SEP-2011' as T1_SD, '21-OCT-2011' as T1_ED,
2 as T2,'31-OCT-2011' as T2_SD, '16-DEC-2011' as T2_ED,
3 as T3,'03-JAN-2012' as T3_SD, '10-FEB-2012' as T3_ED,
4 as T4,'20-FEB-2012' as T4_SD, '30-APR-2012' as T4_ED,
5 as T5,'16-APR-2012' as T5_SD, '01-JUN-2012' as T5_ED
from dual) mytable
aka
TERMS_YEAR             T1                     T1_SD       T1_ED       T2                     T2_SD       T2_ED       T3                     T3_SD       T3_ED       T4                     T4_SD       T4_ED       T5                     T5_SD       T5_ED      
2012                   1                      05-SEP-2011 21-OCT-2011 2                      31-OCT-2011 16-DEC-2011 3                      03-JAN-2012 10-FEB-2012 4                      20-FEB-2012 30-APR-2012 5                      16-APR-2012 01-JUN-2012 into the following 4 columns of data (year, term, term_start, term_end):
select terms_year, term, t1_sd as term_start, t1_ed as term_end from
(select 2012 as terms_year, 1 as term, '05-SEP-2011' as T1_SD, '21-OCT-2011' as T1_ED from dual union all
select 2012 as terms_year, 2 as term, '31-OCT-2011' as T2_SD, '16-DEC-2011' as T2_ED from dual union all
select 2012 as terms_year, 3 as term, '03-JAN-2012' as T3_SD, '10-FEB-2012' as T3_ED from dual union all
select 2012 as terms_year, 4 as term, '20-FEB-2012' as T4_SD, '30-APR-2012' as T4_ED from dual union all
select 2012 as terms_year, 5 as term, '16-APR-2012' as T5_SD, '01-JUN-2012' as T5_ED from dual) mytable
aka
TERMS_YEAR             TERM                   TERM_START  TERM_END   
2012                   1                      05-SEP-2011 21-OCT-2011
2012                   2                      31-OCT-2011 16-DEC-2011
2012                   3                      03-JAN-2012 10-FEB-2012
2012                   4                      20-FEB-2012 30-APR-2012
2012                   5                      16-APR-2012 01-JUN-2012 Much obliged if anyone can teach me how - I can't get my head around the pivot/unpivot syntax! E.g.
Select *
From mytable
UNPIVOT (
unpivot_clause
unpivot_for_clause
unpivot_in_clause)
Thanks,
TP.

Answer 1

Hi,
Using the SELECT ... PIVOT feature:
SELECT       terms_year
,       term
,       term_start
,       term_end
FROM       mytable
UNPIVOT       (  ( term
          , term_start
          , term_end
          )     FOR num_col
             IN ( (t1, t1_sd, t1_ed)     AS 1
             , (t2, t2_sd, t2_ed)     AS 2
             , (t3, t3_sd, t3_ed)     AS 3
             , (t4, t4_sd, t4_ed)     AS 4
             , (t5, t5_sd, t5_ed)     AS 5
ORDER BY  terms_year     -- If needed
,            num_col
;The basic syntax for UNPIVOTing to 1 column (plus a label column) is
UNPIVOT (    outcol
     FOR  label     IN ( incol_1  AS label_val_1
                       , incol_2  AS label_val_2
                  , incol_n  AS label_val_n
     )where
outcol       is the pivoted output column, containing values from the original table,
label       is a label column, which will contain values hard-coded in the query,
incol_1, incol_2, ..., incol_n       are the columns from the origianl table to be unpivoted
label_val_1, label_val_2, ..., label_val_n       are the hard-coded values that will go in the label column.
The syntax for pivoting to m columns (m > 1) is like that for pivoting 1 column, but
instead of outcol, you give a comma-delimited list of m outcols, enclosed in parentheses, and
instead of incol_1, incol_2, ... incol_n, you give a comma-delimited list of m columns, enclosed in parentheses.
By the way, storing dates in VARCHAR2 columns is not a very good idea. Use DATE columns instead.
Edited by: Frank Kulash on Jul 16, 2012 6:11 PM