Question

我有一个包含以下列的表：

agent     status  

A          Mail Sent  
B          Fax Sent  
A          Fax Sent  
B          Mail Sent  
B          Mail Sent  
B          Fax Sent

我想得到这个结果：

Agent  Fax_Count    Mail_Count

A      1            1  
B      2            2

Answer 1

您可以尝试这样的事情

DECLARE @TABLE TABLE(
    agent VARCHAR(10),
    status VARCHAR(10)
)

INSERT INTO @TABLE (agent,status) SELECT 'A','Mail Sent'
INSERT INTO @TABLE (agent,status) SELECT 'B','Fax Sent'
INSERT INTO @TABLE (agent,status) SELECT 'A','Fax Sent'
INSERT INTO @TABLE (agent,status) SELECT 'B','Mail Sent'
INSERT INTO @TABLE (agent,status) SELECT 'B','Mail Sent'
INSERT INTO @TABLE (agent,status) SELECT 'B','Fax Sent' 

SELECT  agent,
        SUM(CASE WHEN status = 'Mail Sent' THEN 1 ELSE 0 END) Mail_Count ,
        SUM(CASE WHEN status = 'Fax Sent' THEN 1 ELSE 0 END) Fax_Count
FROM    @TABLE
GROUP BY agent

Answer 2

作为旁观者（好）解决方案的替代方案：

SELECT  agent,
        (SELECT COUNT(*) FROM myTable WHERE agent = t.agent AND status = 'Mail Sent') Mail_Count,
        (SELECT COUNT(*) FROM myTable WHERE agent = t.agent AND status = 'Fax Sent') Fax_Count
FROM    myTable t
GROUP BY agent

根据数据的分布，性能可能优于他的解决方案（在计算字段上没有SUM）或更差（子选择）或相等（如果查询分析器在两种情况下都找到最佳执行计划）。

Answer 3

  select Name, SUM(MailSent),SUM(FaxSent)
  from 
  (
  select 
   case Status when 'Mail Sent' then 1 else 0 end as MailSent , 
   case Status when 'Fax Sent' then 1 else 0 end as FaxSent  ,
   Name
   from Agents
  ) tmp

Answer 4

你可以做到这一点......可能不是最优雅的但它会起作用...... 只需将@Table换成你正在查询的表......

SELECT DISTINCT
  T.AGENT,
  (SELECT COUNT(AGENT) FROM @TABLE WHERE AGENT = T.AGENT AND Status LIKE 'Fax%') AS Fax_Count,
  (SELECT COUNT(AGENT) FROM @TABLE WHERE AGENT = T.AGENT AND Status LIKE 'Mail%') AS Email_Count
FROM
  @TABLE T

Answer 5

这是使用PIVOT功能解决问题的新方法（自SQL Server 2005起）：

SELECT agent, [Mail Sent] AS Mail_Count, [Fax Sent] AS Fax_Count
FROM 
(
  SELECT T.agent, T.status, COUNT(*) AS Counter
  FROM tblAgents AS T
  GROUP BY T.agent, T.status
) AS Data
PIVOT
(
  SUM(Counter) FOR [status] IN ([Mail Sent], [Fax Sent])
) AS PivotTable

由于语法更复杂，我不经常使用这个，但也许有一些性能可以获得？

用于获取分组项计数的SQL查询

5 个答案: