Sql 按日期间隔选择多行分组（导致重复）

我试图检索一个月前15天和该月后15天的体重数据。 如下表所示

这是我的密码

SELECT  * from

( select SUM(B.SCALE_WEIGHT) as Mtrl1 FROM TRACK2.LOG2_TAB B 
where   B.SCALE_EVENTDATE >= date '2020-09-01' 
and B.SCALE_EVENTDATE < date '2020-09-30' 
AND B.Scale_EVENTDATE = B.SCALE_EVENTDATE 
and MTRLID_EXT = 206
group by  floor(extract(day from SCALE_EVENTDATE)/16)   )  ,


( select SUM(B.SCALE_WEIGHT) as Mtrl2 FROM TRACK2.LOG2_TAB B 
where   B.SCALE_EVENTDATE >= date '2020-09-01' 
and B.SCALE_EVENTDATE < date '2020-09-30' 
AND B.Scale_EVENTDATE = B.SCALE_EVENTDATE 
and MTRLID_EXT = 211 
group by  floor(extract(day from SCALE_EVENTDATE)/16)   ) 

但结果如下图所示，数据重复！和缺少日期列

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我认为您需要条件聚合：

select 
    floor(extract(day from scale_eventdate)/16) as fortnight,
    sum(case when mtrlid_ext = 206 then scale_weight else 0 end) as mtrl1,
    sum(case when mtrlid_ext = 211 then scale_weight else 0 end) as mtrl2
from track2.log2_tab
where   
    mtrlid_ext in (206, 211)
    and scale_eventdate >= date '2020-09-01' 
    and scale_eventdate <  date '2020-10-01' 
group by  floor(extract(day from scale_eventdate) / 16)

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注意，我固定了日期过滤；如果您想要整个9月份，那么第二个条件应该是：请编辑问题并显示TRACK2.LOG2_选项卡和示例数据的定义。