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Oracle Pivot examples

Oracle Tips by Burleson Consulting
August 1,  2008


Question:  Can you please share some examples of using the Oracle SQL pivot operator?

Answer:  The function PIVOT transposes rows in columns and the function UNPIVOT transposes columns in rows. They have been added in 11g. 

WITH
   T
AS
(
   SELECT
      DEPTNO
   FROM
      EMP
)
SELECT
   *
FROM
   T
PIVOT
(
   COUNT(*)
   FOR
      (DEPTNO)
   IN
      (10,20,30,40)
);

        10         20         30         40
---------- ---------- ---------- ----------
         3          5          6          0

----------------------------------------------------------------------------
| Id  | Operation           | Name | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |      |     1 |    52 |     3   (0)| 00:00:01 |
|   1 |  VIEW               |      |     1 |    52 |     3   (0)| 00:00:01 |
|   2 |   SORT AGGREGATE    |      |     1 |     3 |            |          |
|   3 |    TABLE ACCESS FULL| EMP  |    14 |    42 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------


Four columns are created for the departments 10, 20, 30 and 40. For each column, the number of corresponding rows is counted.

Compare with:

SELECT
   DEPTNO,
   COUNT(*)
FROM
   EMP
GROUP BY
   DEPTNO; 

    DEPTNO   COUNT(*)
---------- ----------
        30          6
        20          5
        10          3


In the first statement, one row is returned with all departments. In the second statement each department is on a different row. The columns that are not aggregated and not pivoted will return multiple rows:

WITH
   T
AS
(
   SELECT
      DEPTNO,
      JOB,
      SAL
   FROM
      EMP
)
SELECT
   *
FROM
   T
PIVOT
(
   MIN(SAL) AS MINSAL,
   MAX(SAL) AS MAXSAL
FOR
   (JOB)
IN
   (
      'CLERK' AS CLERK,
      'SALESMAN' AS SALES
   )
)
ORDER BY
   DEPTNO;

    DEPTNO CLERK_MINSAL CLERK_MAXSAL SALES_MINSAL SALES_MAXSAL
---------- ------------ ------------ ------------ ------------
        10         1300         1300
        20          800         1100
        30          950          950         1250         1600

Three rows are selected. The job is the pivot, the salaries are aggregated and the departments are returned as distinct rows. Note the different values for the pivot are explicitly listed.

The inline view T contains three columns, the salary is aggregated, the job is transposed into multiple columns, and the remaining column is used as a group for the aggregation. The remaining column is the department, which contains three distinct values; each value returns exactly one row. To specify the group by the department, it is therefore necessary to select only the department in addition to the aggregated values and to the transposed column.


Here are some working examples of the pivot operator from the book "SQL Design Patterns", highly recommended.  Also see how to pivot rows to columns and pivot columns to rows.

SQL Server 2005 introduced the pivot operator as syntax extension for a table expression in the from clause:

select * from
(Sales pivot (sum(Amount) for Month in (?Jan?, ?Feb?, ?Mar?))

There is nothing like JanCnt in the original data. Indeed there is not, but transforming the month column data into the new column with the Cnt postfix can be done easily with string concatenation. Therefore, the answer to the problem is:

select scount.*, ssum.* from (
select * from (
  (select product, month || ?Cnt?, amount from Sales)
  pivot (count(*) for Month in (?JanCnt?, ?FebCnt?, ?MarCnt?)
) scount, (
select * from (
  (select product, month || ?Sum?, amount from Sales)
  pivot (sum(Amount) for Month in (?JanSum?, ?FebSum?, ?MarSum?)
) ssum
where scount.product = ssum.product

Unpivot in a standard SQL syntax is:

select product, ?Jan? as Month, Jan as Amount from PivotedSales
 union all
select product, ?Feb? as Month, Feb as Amount from PivotedSales
 union all
select product, ?Mar? as Month, Mar as Amount from PivotedSales


Again it is repetitive and not dynamically extensible. In SQL Server 2005 syntax, it becomes:

select * from
(PivotedSales unpivot (Amount for Month in (?Jan?, ?Feb?, ?Mar?))

And here are pivot examples from John Palinski:

The For clause matches the aggregated FK_department values produced by the upper query to the values in the Subquery list.  If a value does not exist in the Subquery list, it is not displayed as a column.
 

select *
from
  (select fk_department
   from employee)
   pivot
    (count(fk_department)
      for fk_department in ('INT', 'WEL', 'CEN', 'POL'));

 

'INT'         'WEL'       'CEN'     'POL'                                                                            
----------    ----------   ----------  ----------                                                                             
        7            6            0          8         

 select * from
  (select current_position, fk_department, wages
   from employee)
   pivot
   (sum(wages)
     for fk_department in ('INT', 'WEL', 'CEN', 'POL'));
 

Department wages by current position view
 

create view pivotTable as
  select *
  from
  (select current_position, fk_department, wages
  from employee)
  pivot
  (sum(wages)
  for fk_department in ('INT' as int, 'WEL' as wel,
   'CEN' as cen, 'POL' as pol));

 

 
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