1、虚拟表与伪列1.1、DUAL 虚拟表Oracle 专属占位表 → Flink 直接省略OracleFlink SQLSELECT SYSDATE FROM DUAL;SELECT 1+1 FROM DUAL;SELECT CURRENT_TIMESTAMP;SELECT 1+1;Flink SQL 支持无 FROM 子句的 SELECT，DUAL 直接删除即可。1.2、ROWNUM 伪列行号限制 → ROW_NUMBER() 窗口函数OracleFlink SQLSELECT * FROM tWHERE ROWNUMSELECT * FROM (SELECT *, ROW_NUMBER() OVER(ORDER BY proctime) AS rnFROM t) WHE