把一些类别作为列名

Question

我有一个 table 看起来像这样：

Month	Region	Category	Size	Brand	Price
January	Canada	T-shirts	S	Nike	100
January	Canada	T-shirts	S	Reebok	150
January	Canada	T-shirts	S	Puma	200
January	Canada	Jacket	S	Nike	200
January	Canada	Jacket	S	Reebok	300
January	USA	Jacket	L	Puma	400
January	USA	Jacket	L	Reebok	500

我想让 table 看起来像这样（不需要聚合函数）：

Month	Region	Category	Size	Nike	Reebok	Puma
January	Canada	T-shirts	S	100	150	200
January	Canada	Jacket	S	400	300	NULL
January	USA	Jacket	L	NULL	500	400

我想要 select 具有相同月份、地区、类别和尺码值的行，耐克价格高于其他任何价格。对于 table 上面的结果应该是：

Month	Region	Category	Size	Nike	Reebok	Puma
January	Canada	Jacket	S	400	300	NULL

Answer 1

您似乎需要条件聚合然后进行一些过滤。

select *
from (select Month, Region, Category, Size,  
             max(case when brand = 'Nike' then price end) as nike, 
             max(case when brand = 'Reebok' then price end) as Reebok, 
             max(case when brand = 'Puma' then price end) as Puma           
      from t
      group by Month, Region, Category, Size
     ) t
where nike > coalesce(Reebok, 0) and
      nike > coalesce(Puma, 0);

把一些类别作为列名

Put some categories as column names

sql

sql-server

sql-server-2008