DB2 字符串的字段转为整形时的问题

正确语句：

select int(cast(substr(dpt_leader_ids,4,posstr(dpt_leader_ids,',0)')-4) as varchar(8))), d.* from zm_plan_day p left join pub_dpt d on p.dpt_id = d.organ_id where id = 'PD00001880';

错误语句(少了cast转换varchar)：

select int(substr(dpt_leader_ids,4,posstr(dpt_leader_ids,',0)')-4))), d.* from zm_plan_day p left join pub_dpt d on p.dpt_id = d.organ_id where id = 'PD00001880';