Sorting with Name

Question

hi
i have procedure with sorting technic..
for sorting i have used code like this
......select ...... .. select ......  rownum rn from table_name
                         where cond...
         where pagenumber ......  pagesize........
but now i want display result according to sorting,
with alphabetic sorting.
means if a user want to search name like start with name "M"
i want to display result with starting letter is "M" as follows...
and also user want to move <<next> <<last>> <<first>> <previouse>>for this any doc's or sample example or any ideas
Edited by: OraclePLSQL on Dec 30, 2010 5:31 PM

Answer 1

Hi,
ROWNUM shows the order in which a row was received.
If the source of the data is a table, then the order is undefined, and ROWNUM is arbitrary.
If the source of the data is a sub-query or a view, then ROWNUM reflects the ORDER BY clause of that sub-query or view. If there is no ORDER BY clause, then ROWNUM is arbitrarty.
If you want a Pagination Query , where you each page has a given size (it looks like 3 in your example), and you want to display only one given page (page #2 in your example), then you can use ROWNUM, but assign ROWNUM after the data is ordered.
So you could modify the query you posted like this:
SELECT * FROM
   SELECT ENAME,    EMPNO,    SAL
   ,      ROWNUM   AS RN               -- ROWNUM is meaningful here (source is ordered)
   FROM
     SELECT    ENAME, EMPNO, SAL          -- No ROWNUM here (source is not ordered)
     FROM      EMP
--   WHERE     ename     LIKE 'M%'          -- Any filtering goes here
     ORDER BY  ename
   WHERE ROWNUM <((2*3)+1)
WHERE RN >= (((2-1)*3)+1)
ORDER BY  rn
;Remember to use an ORDER BY clause in the main query, if you want the output sorted.
Output (using scott.emp):
ENAME           EMPNO        SAL         RN
CLARK            7782       2450          4
FORD             7902       3000          5
JAMES            7900        950          6This is the 2nd page; ADAMS, ALLEN and BLAKE would be on page 1.
I think the analytic ROW_NUMBER function is better than ROWNUM for this kind of thing.
Also, consider using variables instead of the "magic numbers" 2 and 3 in your WHERE clauses.
The following query produces the same results as the query above:
-- How many rows should appear on each page (except maybe the last page)?
VARIABLE  page_size     NUMBER
EXEC  :page_size := 3;
-- Which page do we want to display in this query?
VARIABLE  page_num     NUMBER
EXEC  :page_num  := 2;
WITH     got_rn     AS
     SELECT     ename, empno, sal
     ,     ROW_NUMBER () OVER (ORDER BY ename)     AS rn
     FROM     emp
--     WHERE     ename     LIKE 'M%'     -- Any filtering goes here
SELECT       *
FROM       got_rn
WHERE       CEIL (rn / :page_size)     = :page_num
ORDER BY  rn
;