如何以最高性能查询DB2中的数据范围？ [英] How to query range of data in DB2 with highest performance?

问题描述

通常，我需要从某个范围的表中检索数据;例如，针对每个搜索结果的单独页面。在MySQL我使用LIMIT关键字，但在DB2我不知道。现在我使用此查询来检索数据范围。

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

但我知道这是坏的风格。

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

推荐答案

我的要求已经被添加到DB2 9.7.2中了。

My requirement have been added into DB2 9.7.2 already.

DB2 9.7.2为限制查询结果添加了新语法，如下所示：

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

SELECT * FROM TABLE LIMIT 5 OFFSET 20

21 - 25

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

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