sql - DB2 SQL 错误代码 -255

Question

我以前从未见过此错误代码，也找不到任何文档。这是查询：

WITH QUERY AS (
    SELECT rrn(T1), blah, bleh, 
        ROW_NUMBER() OVER (order by  bleh desc) AS RN  
    FROM T1 
    WHERE (
        upper(blah) like ('%WEST%') 
     OR upper(bleh) like ('%WEST%')
    ) 
) 
SELECT * FROM QUERY WHERE RN BETWEEN 1 AND 10

该错误仅在应用 upper() 时发生。

错误消息是“查询不支持功能”。