我试图找到“id_case”（这里id_case是数字）为空或小于1的值，但得到“ORA-01722：invalid number“，查询如下：

SELECT v.id, v.id_case_p, v.id_case FROM (
SELECT p.id, to_number(replace(p.description,'xyy_','')) as id_case_p, c.id as id_case 
FROM t_processes p left join t_cases c on to_number(replace(p.description,'xyz_','')) = c.id 
where p.active ='Y' and p.id_process_step < 10 
)v 
WHERE v.id_case < 1
;

我也试过下面的方法，但还是出现了同样的错误。

SELECT v.id, v.id_case_p, v.id_case FROM (
    SELECT p.id, to_number(replace(p.description,'xyy_','')) as id_case_p, c.id as id_case 
    FROM t_processes p left join t_cases c on to_number(replace(p.description,'xyz_','')) = c.id 
    where p.active ='Y' and p.id_process_step < 10 
    )v 
    WHERE v.id_case is null
    ;

任何线索都将不胜感激。