Oracle SQL: displaying multiple column values per row Oracle Tips by Burleson Consulting

Oracle SQL does not have a direct mechanism for allowing multiple values from the same column to be displayed in the same row of output.  SQL is designed not to disallow repeating values on a single line of output, but Oracle has several tricks for allowing repeating groups of same-column values on a single line of output.  For example, assume that we need to display all degrees for an employee on a single row of SQL*Plus output:

Jones:  BA Art History, MBA in Finance, PhD in business
Smith:  BS in computer science
Baker:  BBA in Business administration, MS in computer science

Approaches to display many columns on one line of output

Let's take a look at how we can consolidate multiple values into a single-row display.

 - Download Oracle data into Excel Pivot tables
 - Write a PL/SQL function
 - Use the SYS_CONNECT_BY_PATH operator
 - Use Oracle Cross Join

Let's look at each method to consolidate data from a table onto a single row.

Download data into Excel spreadsheet pivot table

Excel spreadsheets are a great way to pivot and analyze Oracle data, and tools like Excel-DB provide a fast API for downloading Oracle data into spreadsheets. Using Excel pivot tables with Oracle data is a fast, easy way to use Oracle business intelligence without buying expensive OLAP solutions (Hyperion, Oracle BI Suite).  Here is an example.

Write a PL/SQL function

You can write a PL/SQL function to display multiple rows values on a single line.  Martin Chadderton has written a Pl/SQL function called "stragg" that you can define to display multiple SQL rows on one single line.  Once defined, you embed the function within your SQL to display your output on a single line:
 

select stragg(ename) from emp;

Smith, Jones, Baker

Use the SYS_CONNECT_BY_PATH operator

This article by Younes Naguib describes how to display multiple values from a single column in a single output row.  In his example, he displays multiple values of the last name column on a single row.  Note his use of the sys_connect_by_path and over operators:

select
   deptno,
   substr(SYS_CONNECT_BY_PATH(lname, ','),2) name_list
from
   (
   select
     lname,
     deptno,
     count(*) OVER ( partition by deptno ) cnt,
     ROW_NUMBER () OVER ( partition by deptno order by lname) seq
   from
     igribun.emp
   where
     deptno is not null)
where
   seq=cnt
start with
   seq=1
connect by prior
   seq+1=seq
and prior
   deptno=deptno;

DEPTNO NAME_LIST
1      Komers,Mokrel,Stenko
2      Hung,Tong
3      Hamer
4      Mansur

 

Use a Cross join

Matt contributed this handy SQL techniques to pivot one row of several columns into a single column with several row, using the Oracle Cross join syntax.  Matt notes that the Cross join "has other uses in conjunction with a WHERE clause to create triangular result sets for rolling totals etc (though thanks to analytic functions those things are very nice and easy)".

SELECT
  ite,
  case
    when ite = 'item1' then item1
    when ite = 'item2' then item2
    when ite = 'item3' then item3
  end as val
FROM
(
  SELECT
    pivoter.ite,
    item1,
    item2,
    item3
  FROM
    someTable
    CROSS JOIN
    (
      select 'item1' as ite from dual
      UNION ALL
      select 'item2' as ite from dual
      UNION ALL
      select 'item3' as ite from dual
    )pivoter
)

Oracle analytic Lag-Over Function

Analytic functions have a pronounced performance improvement since they avoid an expensive self-join and only make one full-table scan to get the results.  This site shows an example of using the Oracle LAG function to display multiple rows on a single column:

SELECT    
   ename,   
   hiredate,sal,LAG (sal, 1, 0)   
   OVER (ORDER BY hiredate) AS PrevSal
FROM    
   emp
WHERE
    job = 'CLERK';

---

My Notes:

For more SQL tips and tricks, see the book "Easy Oracle SQL".  Also see these related notes on SQL output display consolidation:

• pivoting one row of several columns into one column of several rows.
   
• Display and sort output on a single line

If you like Oracle tuning, see the book "Oracle Tuning: The Definitive Reference", with 950 pages of tuning tips and scripts.  You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.