GROUP_CONCAT

Question

나는 테이블이 포함 된이 ~ 같은 백만 항목 :

customer_id | purchased_at  | product 
1   | 2012-06-01 00:00 | apples 
1   | 2012-09-02 00:00 | apples 
1   | 2012-10-01 00:00 | pears 
2   | 2012-06-01 00:00 | apples 
2   | 2012-07-01 00:00 | apples 
3   | 2012-09-02 00:00 | pears 
3   | 2012-10-01 00:00 | apples 
3   | 2012-10-01 01:00 | bananas 

내가 한 행, DISTINCT로하고 purchased_at

의 순서로 제품을 연결하려면

MySQL의에서 그냥 얻을

select customer_id, min(purchased_at) as first_purchased_at, 
group_concat(DISTINCT product order by purchased_at) as all_purchased_products 
from purchases group by customer_id; 

를 사용

customer_id | first_purchased_at | all_purchased_products 
1   | 2012-06-01 00:00 | apples, pears 
2   | 2012-06-01 00:00 | apples 
3   | 2012-09-02 00:00 | pears, apples, bananas 

SQL Server 2012에서 어떻게 할 수 있습니까?

나는 일 다음 '해킹'을 시도하지만 잔인한의 긴 테이블

select 
customer_id, 
min(purchased_at) as first_purchased_at, 
stuff ((select ',' + p3.product 
      from (select p2.product, p2.purchased_at, 
      row_number() over(partition by p2.product order by p2.purchased_at) as seq 
      from purchases p2 where 
      p2.customer_id = p1.customer_id) p3 
      where p3.seq = 1 order by p3.purchased_at 
      for XML PATH('')), 1,1,'') AS all_purchased_products 
from purchases p1 
group by customer_id; 

나는이 문제를 해결하기 위해 무엇을 할 수에서 잘 수행하지 않습니다?

Answer 1

나는이 빨리 될 것입니다 있는지 확실하지 않습니다,하지만 여기 당신이 STUFF()에 두 번 purchases에 참여하지 않는 다른 버전 :

select customer_id, 
    min(purchased_at) as first_purchased_at, 
    stuff ((select ',' + p2.product 
      from 
      (
      select product, customer_id, 
       ROW_NUMBER() over(partition by customer_id, product order by purchased_at) rn, 
       ROW_NUMBER() over(partition by customer_id order by purchased_at) rnk 
      from purchases 
     ) p2 
      where p2.customer_id = p1.customer_id 
      and p2.rn = 1 
      group by p2.product, rn, rnk 
      order by rnk 
      for XML PATH('')), 1,1,'') AS all_purchased_products 
from purchases p1 
group by customer_id; 

참조 SQL Fiddle with Demo

결과 :

| CUSTOMER_ID |    FIRST_PURCHASED_AT | ALL_PURCHASED_PRODUCTS | 
--------------------------------------------------------------------------- 
|   1 |  June, 01 2012 00:00:00+0000 |   apples,pears | 
|   2 |  June, 01 2012 00:00:00+0000 |     apples | 
|   3 | September, 02 2012 00:00:00+0000 | pears,apples,bananas |