如何排查IBM/DB2 SQL0104 Token无效问题？

本人主要从事Microsoft SQL开发，在运行以下IBM/DB2 SQL语句时触发了SQL0104错误：

SELECT
    Test_Data.PRDINVSEQ.DASTAT, 
    DACUST, 
    DASRNO, 
    DADTOR, 
    DAORNO, 
    Test_Data.bthdrextpf.SHXDEP, 
    DADNAM, 
    DADTST, 
    CASE WHEN DACONF = '' THEN 'N' ELSE DACONF END AS DACONF1, 
    DAENGD, 
    DAEXTC, 
    DAPRGY, 
    Test_Data.BTHDR.SHSPL1, 
    DASPRD, 
    DADTCD, 
    DALDNO, 
    DADTLD, 
    DADTMD, 
    DAMDLN, 
    Test_Data.PRDINVSEQ.STATSQ
FROM Test_Data.BTHDR 
JOIN Test_Data.DLRINVAPF ON SHORNO = DAORNO 
JOIN Test_Data.PRDINVSEQ ON Test_Data.DLRINVAPF.DASTAT = Test_Data.PRDINVSEQ.DASTAT 
JOIN Test_Data.BTHDREXTPF ON SHORNO = SHXORNO 
WHERE  TRIM(DACUST)<>'' AND Test_Data.DLRINVAPF.DASTAT IN ('WP', 'OD', 'SC', 'BO')
ORDER BY DADNAM, Test_Data.PRDINVSEQ.STATSQ ASC, DADTST ASC, DAMDLN ASC 

错误提示如下：

[SQL0104] Token   was not valid. Valid tokens: ( + * -? : DAY INF LAG NAN RID ROW RRN CASE CAST CHAR DATE DAYS.

注意到错误信息里“Token”和“was”之间有三个空格，说明DB2解析时识别到了一个无法显示的无效字符。经过对比排查，确认问题出在SQL语句末尾存在非打印字符，将这些字符删除后，语句可以正常执行。

内容的提问来源于stack exchange，提问作者user153923