pb中sql语句用to_char查询出来数据，居然无法检索出数据，oracle数据库，这是什么原因?

/*这样dw_modified总是无法检索出正确的结果*/
select nvl(max(to_char(SBLJL01,'000')),'000') 
  into :is_recoder_old_sn 
  from emra03 
 where szybh01 = :as_pat_id
   and Swdfl01 = :as_emr_code;    

Integer li_ret
li_ret = dw_modified.retrieve(as_pat_id,as_emr_code,is_recoder_old_sn)

/*这样就没事，能得出结果*/
select max(SBLJL01)
into :is_recoder_old_sn 
from emra03 
where szybh01 = :as_pat_id
and Swdfl01 = :as_emr_code;    

Integer li_ret
li_ret = dw_modified.retrieve(as_pat_id,as_emr_code,is_recoder_old_sn)

/*这样也没问题*/
Long ll_recoder_old_sn  
select max(to_number(SBLJL01))
  into :ll_recoder_old_sn  
  from emra03 
 where szybh01 = :as_pat_id
   and Swdfl01 = :as_emr_code;
    
is_recoder_old_sn = String(ll_recoder_old_sn,"000")

Integer li_ret
li_ret = dw_modified.retrieve(as_pat_id,as_emr_code,is_recoder_old_sn)

可是两个select 语句的结果都是023,奇怪不？