Question

我有以下数据。

输出：

id  cid price   sold
--------------------
 1  1   10      20     
 2  1   30      40      
 3  2   50      60

我需要的是：

 id cid Amount
--------------
  1 1   20     
  2 1   10      
  3 2   30

如果id = cid然后以其他方式出售

如果id != cid则将cid的匹配ID的价格作为金额（请参考上面的输出，如果它令人困惑！）

我有以下SQL查询：

 declare @tg table(id int, cid int, price int, sold int)

 insert into @tg values(1, 1, 10, 20); 
 insert into @tg values(2, 1, 30, 40);
 insert into @tg values(3, 2, 50, 60);

SELECT 
    id, cid, 
    CASE WHEN id  = cid 
           THEN sold 
         WHEN B.id IN (SELECT 
                           CASE WHEN id != cid 
                                THEN cid 
                           END AS cid1 
                       FROM @tg A 
                       WHERE A.cid = B.id) 
           THEN price  
    END as amount 
FROM 
    @tg AS B
 --OR
select
id,cid,
CASE WHEN id  = cid THEN sold else price END as amount from @tg
 as B

id != cid时无效。

Answer 1

select id,cid,case when id=cid then sold else (select price from @tg t1 where t1.id = t2.cid) end as amount
from @tg t2

我认为那就是你要找的东西，如果id = cid卖掉了，否则＆gt;从销售表中获取相应的价格，其中cid = id

Answer 2

像这样修改SELECT

select  id,cid, CASE WHEN id  = cid THEN sold 
  WHEN id  <>  cid 
      THEN price  
      END as amount from @tg
 as B

这将在id = cid其他明智Prize

时返回销售

Answer 3

select 
  id, 
  cid, 
  case when cid = id then sold 
    else (select price from @tg where id=c.cid )
  end as amount  
from @tg c

Answer 4

我认为这更像是一个加入：

$ curl -H 'Host: git.niklasrosenstein.com' http://localhost:8080 -i
HTTP/1.1 302 Found
Date: Mon, 18 Jan 2016 14:29:08 GMT
Status: 302 Found
Connection: close
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Location: http://niklasrosenstein.com
Content-Type: text/html; charset=utf-8
Cache-Control: no-cache
X-Request-Id: 1a63e4a4-a5fe-4544-8f74-8b1bd0117a57
X-Runtime: 0.271394

<html><body>You are being <a href="http://niklasrosenstein.com">redirected</a>.</body></html>

您只是在同一个表中查找该值。您实际上并不需要将select tg.*, tgc.price as sold from @tg tg left join @tg tgc on tg.cid = tgc.id;短路。

或者，如果您更喜欢子查询：

join

在这两种情况下，使用表别名很重要。否则，您无法区分临时表。

案例表达式中的子查询

4 个答案: