为什么会出现双倍的列名呢(ORACAL数据库)

SELECT '当日' as types,a.xmthdlx,count(1) as n FROM

(select

requestid,

czrq,

jxs,

czmc,

case when hdlx = '1' then '车展' else to_char(hdlx) end as hdlx,

case when xmthdlx = '1' then '小红书'

when xmthdlx = '0' then '抖音'

else to_char(xmthdlx) end as xmthdlx

from formtable_main_40

where czrq = '${dates}') a

INNER JOIN 

(

select requestid,workflowid,status from workflow_requestbase

where 1=1

-- and (status = '出口7' or status = '结束')

and (workflowid = 3022 OR workflowid = 42022) ) b

ON a.requestid = b.requestid

group by a.xmthdlx

union ALL

SELECT '当月' as types,a.xmthdlx,count(1) as n FROM

(select

requestid,

czrq,

jxs,

czmc,

case when hdlx = '1' then '车展' else to_char(hdlx) end as hdlx,

case when xmthdlx = '1' then '小红书'

when xmthdlx = '0' then '抖音'

when xmthdlx = '2' then '微信'

else to_char(xmthdlx) end as xmthdlx

from formtable_main_40

where czrq >=  to_char(TO_DATE('${dates}','YYYY-MM-DD'),'yyyy-mm-')||'01') a

INNER JOIN 

(

select requestid,workflowid,status from workflow_requestbase

where 1=1

-- and (status = '出口7' or status = '结束')

and ( workflowid = 3022  OR workflowid = 42022) 

) b

ON a.requestid = b.requestid

group by a.xmthdlx

union ALL

SELECT '累计' as types,a.xmthdlx,count(1) as n FROM

(select

requestid,

czrq,

jxs,

czmc,

case when hdlx = '1' then '车展' else to_char(hdlx) end as hdlx,

case when xmthdlx = '1' then '小红书'

when xmthdlx = '0' then '抖音'

when xmthdlx = '2' then '微信'

else to_char(xmthdlx) end as xmthdlx

from formtable_main_40

-- where czrq >=  to_char(TO_DATE('${dates}','YYYY-MM-DD'),'yyyy-mm-')||'01'

) a

INNER JOIN 

(

select requestid,workflowid,status from workflow_requestbase

where 1=1

-- and (status = '出口7' or status = '结束')

and ( workflowid = 3022  OR workflowid = 42022) 

) b

ON a.requestid = b.requestid

group by a.xmthdlx