使用Netezza中的新值更新列

Question

我对解决这个问题有疑问。我的表具有型号名称，设备类型，计数设备类型和NEW_device_type。我想将每个模型的当前device_type列更新为只有一个device_type（请参见表中的示例）

**MODEL               DEVICE_TYPE    COUNT_DEVICE_TYPE          NEW_DEVICE_TYPE**

SAMUNG GALAXY S5      SMARTPHONE             100                SMARTPHONE
SAMUNG GALAXY S5      PORTABLE PDA           30                 SMARTPHONE
SAMUNG GALAXY S5      HANDHELD               10                 SMARTPHONE

我已经尝试过此代码，但是无法捕获新值：

select
model
,device_type
,case when count(model)<40 then 
(select distinct device_type from tmp_BI_dim_device_ref a group by model, device_type having count(model)>10 ) else device_type end as new_device_type
from tmp_BI_device_table
group by 1,2

我收到此错误：

ERROR:  12 : More than one tuple returned by a subselect used as an expression

Answer 1

如果要使用最高数量的设备类型，则可以使用first_value()：

select model, device_type, count(*),
       first_value(device_type) over (partition by model order by count(*) desc) as imputed_device_type
from tmp_BI_device_table
group by 1, 2