Oracle存储过程游标循环更新新增字段处理线上历史数据问题

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">新增生效时间字段，对于新单此字段有值，对于历史数据此字段无值，查询不到相关历史数据问题</span>

CREATE OR REPLACE PROCEDURE pr_update_FIRSTLOCALE_EFFECTTM
declare
cursor cur_emp is select REACH_TM,FL_ID  from  T_AB_FIRSTLOCALE where REACH_TM is not null;
begin
--更新游标1
vcount:=0;
open cur_emp;
for return_cur in cur_emp
loop
update T_AB_FIRSTLOCALE
set EFFECT_TM = cur_emp.REACH_TM
where FL_ID=cur_emp.FL_ID;

if mod(vcount,500)=0 then
commit;
end if;
vcount:=vcount+1;
end if;
end loop;
close cur_emp;
Exception
When others then
Rollback;
end;