Fuangwith S. Fuangwith S. - 1 month ago 13
SQL Question

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

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

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 OFFSET 20

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

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