如何解决SQL(Impala)- 查找重复值,包括空值
我有一个名为 baseTable 的表,其中包含许多列,但是我使用了 3 个名为 Material_Type、Material_Desc(具有空值)、Material_Number 的列来使用 row_num 和 partition by 查找重复项。 注意:我需要根据 3 个条件过滤重复项。
- 当 Material_Type = Material_Type 时
- 当 Material_Desc = Material_Desc
- 当 Material_Number Material_Number
示例表:
Material_Type Material_Desc Material_Number
ABC XYZ 1
ABC XYZ 1
ABC XYZ 2
ABC XYZ 3
DEF IMM 1
LMN NULL 1
LMN NULL 2
我只想在 newTable 中有重复的值并想删除不同的值。
所需的输出:
Material_Type Material_Desc Material_Number new
ABC XYZ 1 1
ABC XYZ 1 2
ABC XYZ 2 3
ABC XYZ 3 4
LMN NULL 1 1
LMN NULL 2 2
我使用了下面的查询,但没有得到预期的输出,因为它不包括 Material_Desc 列中的空值,并且没有使用 Null 进行分区,还创建了不需要的重复记录。
使用的查询:
create table newTable as
with mycte as
(
select
m.MATERIAL_NUMBER,m.MATERIAL_TYPE,m.Material_Desc,row_number() over(partition BY d.MATERIAL_TYPE,d.Material_Desc order by d.MATERIAL_NUMBER) as new
from baseTable m
inner join
(
select MATERIAL_NUMBER,MATERIAL_TYPE,Material_Desc,count(*) from baseTable group by
MATERIAL_NUMBER,Material_Desc having count(*) > 1
) d on d.MATERIAL_NUMBER <> m.MATERIAL_NUMBER and d.MATERIAL_TYPE=m.MATERIAL_TYPE
and d.Material_Desc= m.Material_Desc)
select * from mycte
任何帮助将不胜感激。
解决方法
只需使用 row_number()
和 count(*)
作为窗口函数:
select Material_Type,Material_Desc,Material_Number,row_number() over (partition by Material_Type,Material_Desc order by Material_Number) as new
from (select t.*,count(*) over (partition by Material_Type,Material_Desc) as cnt
from t
) t
where cnt > 1;
这适用于您提供的数据,只需计算每种类型和描述的行数即可。如果您确实需要不同的材料编号,一种方法是 min()
和 max()
:
select Material_Type,Material_Desc order by Material_Number) as new
from (select t.*,min(Material_Number) over (partition by Material_Type,Material_Desc) as min_Material_Number,max(Material_Number) over (partition by Material_Type,Material_Desc) as max_Material_Number
from t
) t
where min_Material_Number <> max_Material_Number;
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