How to query range of data in DB2 with highest performance?

Question

Usually, I need to retrieve data from a table in some range; for example, a separate page for each search result. In MySQL I use LIMIT keyword but in DB2 I don't know. Now I use this query for retrieve range of data.

SELECT * 
FROM(
   SELECT  
      SMALLINT(RANK() OVER(ORDER BY NAME DESC)) AS RUNNING_NO
      , DATA_KEY_VALUE
      , SHOW_PRIORITY
   FROM 
      EMPLOYEE
   WHERE 
      NAME LIKE 'DEL%'
   ORDER BY
      NAME DESC
   FETCH FIRST 20 ROWS ONLY
) AS TMP
ORDER BY 
  TMP.RUNNING_NO ASC
FETCH FIRST 10 ROWS ONLY

but I know it's bad style. So, how to query for highest performance?

Answer 1

Not sure why you are creating the TMP table. Isn't RUNNING_NO aready in ascending sequence? I would think:

SELECT SMALLINT(RANK() OVER(ORDER BY NAME DESC)) AS RUNNING_NO,
       DATA_KEY_VALUE,
       SHOW_PRIORITY
  FROM EMPLOYEE
 WHERE NAME LIKE 'DEL%'
 ORDER BY NAME DESC
 FETCH FIRST 10 ROWS ONLY

would give the same results.

Having an INDEX over NAME on the EMPLOYEE table will boost performance of this query.

Answer 2

My requirement have been added into DB2 9.7.2 already.

DB2 9.7.2 adds new syntax for limit query result as illustrate below:

SELECT * FROM TABLE LIMIT 5 AND 20

the database will retrieve result from row no. 21 - 25