hiveSQL关于left join后，出来空值

数据库 hiveSQL
主表vi left join 副表 cld，主表里的party_id全部不为空值，但是最后left join后出来的party_id有空值，这是为什么？
select
'D0' data_area,
vi.inst_soc_no inst_soc_no,
cast(vi.party_id as int) party_id,
'10' vip_code,
vi.admittance_type admittance_type
from (select * from pa_old.old_e_ecif_vip_info_rocrm_h_20231201) vi
left join (select data_area,
v_inst_soc_no inst_soc_no,
n_cust_ref_code party_id
from pa_old.old_edp_fsw_cust_level_detail_h_20240131
where v_cust_level_type_cd = 'FINAL') cld
on cast(vi.party_id as int) = cast(cld.party_id as int)#SQL##hivesql##数据库##left join##join#
;