在 SQL 或 LINQ 中根据月份对三个表中的条目进行计数

Question

我想从 SQL Server 2005 数据库中的三个表中提取一些数据。虽然这肯定可以在代码中完成，但似乎可以在 SQL 中相当好地完成（LINQ 的加分！）。

基本上，我想知道每个月每个员工与我们的每个客户进行了多少次通话和会议。像这样：

Employee GUID   Customer GUID   Jan calls   Jan mtgs   Feb calls      Feb mtgs...
[a guid]        [another guid]  5           0          7              3

数据分布在三个表中。为了简单起见，我们只显示相关列：

通讯表

[CommunicationId]  (PK, uniqueidentifier)
[Type]             (nvarchar(1)) ('C' for call, 'M' for meeting, etc.)
[Date]             (datetime)

人员通讯表

[PersonId]         (PK, FK, uniqueidentifier) (Can contain GUIDs for employees or clients, see Person Table below)
[CommunicationId]  (PK, FK, uniqueidentifier)

人员表

[PersonId]         (PK, uniqueidentifier)
[Type]             (nvarchar(1)) ('E' for employee, 'C' for customer)

因此，问题：

1. 可以在 SQL 中完成此操作，而不会出现可怕的代码或大的性能问题吗？
2. 如果是这样，怎么办？我什至愿意制定一个好的高级策略。我猜测 枢轴 将在这里发挥重要作用（特别是“复杂的 PIVOT 示例”）。 DATEPART(MONTH, Date) 似乎是一种很好的分区方法按月进行的通信，大致如下：

选择日期部分（月份，日期），计数（*） 
来自 [通讯表]
WHERE DATEPART（年份，日期）= '2009'
按日期部分分组（月、日）
按日期部分排序（月、日）

...这让我得到 2009 年每个月的通信数量：

1    2871
2    2639
3    3654
4    2751
5    1773
6    2575
7    2906
8    2398
9    2621
10   2638
11   1705
12   2290

Answer 1

非 PIVOT、CASE 使用语法：

WITH summary AS (
      SELECT emp.personid AS emp_guid,
             cust.personid AS cust_guid,
             DATEPART(MONTH, ct.date) AS mon, 
             ct.type,
             COUNT(*) AS num_count
        FROM COMMUNICATIONTABLE ct
   LEFT JOIN PERSON_COMMUNICATION pc ON pc.communicationid = ct.communicationid
        JOIN PERSON emp ON emp.personid = pc.personid
                       AND emp.type = 'E'
        JOIN PERSON cust ON cust.personid = p.personid
                        AND cust.type = 'C'
       WHERE ct.date BETWEEN '2009-01-01' AND '2009-12-31'
    GROUP BY emp.personid, cust.personid, DATEPART(MONTH, ct.ate), ct.type)
SELECT s.emp_guid,
       s.cust_guid,
       MAX(CASE WHEN s.mon = 1 AND s.type = 'C' THEN s.num_count ELSE 0 END) AS "Jan calls",
       MAX(CASE WHEN s.mon = 1 AND s.type = 'M' THEN s.num_count ELSE 0 END) AS "Jan mtgs",
       ... --Copy/Paste two lines, update the month check... and the col alias
  FROM summary s
GROUP BY s.emp_guid, s.cust_guid

使用 WHERE ct.date BETWEEN '2009-01-01' AND '2009-12-31' 因为 WHERE DATEPART(YEAR, Date) = '2009'如果 date 列中存在索引，则 无法使用索引。

Answer 2

这应该可以帮助您开始，我为您做了一年一个月，您还可以添加日期范围限制：

SELECT PE.PersonID as EmployeeID,PC2.PersonID as CustomerID,
 SUM(CASE WHEN DATEPART(MONTH, C.[Date]) = 1 
           AND DATEPART(YEAR,C.[Date]) = 2009 
           AND C.[type] = 'C' THEN 1 ELSE 0 END) AS [Jan 2009 Calls]
FROM PersonTable PE
JOIN PersonCommunicationTable PC ON PE.PersonID = PC.PersonID
JOIN CommunicationsTable C ON PC.CommunicationID = C.CommunicationID
JOIN PersonCommunicationTable PC2 ON PC.CommunicationID = PC2.CommunicationID AND NOT PC2.PersonID = PC.PersonID 
WHERE PE.Type = 'E'

Answer 3

这是使用 Pivot 的相当等效的解决方案。

Declare @Comm TABLE
(
    [CommunicationId] uniqueidentifier PRIMARY KEY DEFAULT NEWID(),
    [Type]  nvarchar(1), -- ('C' for call, 'M' for meeting, etc.)
    [Date] datetime
)

Declare @Person TABLE
(
    [PersonId]  uniqueidentifier PRIMARY KEY DEFAULT NEWID(),
    [Type]      Nvarchar(1) -- ('E' for employee, 'C' for customer)
)
Declare @PersonComm TABLE
(
    [PersonId] uniqueidentifier, -- (Can contain GUIDs for employees or clients, see Person Table below)
    [CommunicationId] uniqueidentifier
)

INSERT INTO @Person(Type)
Select 'C' UNION ALL Select 'E'  UNION ALL Select 'C' UNION ALL Select 'E'

INSERT INTO @Comm([Type],[Date])
Select 'C', '01/04/2010' UNION ALL Select 'C', '01/04/2010'
UNION ALL Select 'C', '04/04/2010' UNION ALL Select 'C', '05/01/2010'
UNION ALL Select 'C', '08/04/2009' UNION ALL Select 'C', '09/01/2009'
UNION ALL Select 'M', '01/04/2010' UNION ALL Select 'M', '03/20/2010'
UNION ALL Select 'M', '04/04/2010' UNION ALL Select 'M', '06/01/2010'
UNION ALL Select 'M', '04/10/2009' UNION ALL Select 'M', '04/10/2009'

INSERT INTO @PersonComm
Select  E.PersonID ,  Comm.[CommunicationId]
FROM    @Person E 
        ,@Comm Comm
Where E.[Type] = 'E' 

INSERT INTO @PersonComm
Select  E.PersonID ,  Comm.[CommunicationId]
FROM    @Person E 
        ,@Comm Comm
Where E.[Type] = 'C' 

Select  EmployeeID, 
        ClientID,
        Year, 
        [JanuaryC] AS [Jan Calls], 
        [JanuaryM] AS [Jan Meetings],
        [FebruaryC], 
        [FebruaryM],
        [MarchC], 
        [MarchM], 
        [AprilC], 
        [AprilM], 
        [MayC], 
        [MayM], 
        [JuneC], 
        [JuneM], 
        [JulyC], 
        [JulyM],
        [AugustC], 
        [AugustM],
        [SeptemberC] ,
        [SeptemberM],
        [OctoberC] ,
        [OctoberM],
        [NovemberC],
        [NovemberM],
        [DecemberC], 
        [DecemberM]

FROM 
(
Select P.PersonId EmployeeID, Client.PersonId ClientID, YEAR(C.Date) Year, DateName(m,C.Date) Month,  COUNT(*) Amount, C.Type CommType,
       DateName(m,C.Date) + C.Type PivotColumn -- JanuaryC
FROM    @Comm C
        INNER JOIN @PersonComm PC
            ON PC.CommunicationId = C.CommunicationId
        INNER JOIN @Person P
            ON P.PersonId = PC.PersonId 
        INNER JOIN @PersonComm PCC
            ON PCC.CommunicationId = PC.CommunicationId
        INNER JOIN @Person Client
            ON Client.PersonId = PCC.PersonId AND Client.Type = 'C' 
Where P.Type = 'E'      
Group By P.PersonId, CLient.PersonId, YEAR(C.Date), DateName(m,C.Date), C.Type
) SourceTable
PIVOT (
MAX(Amount)
FOR PivotColumn IN 
    ([JanuaryC], [JanuaryM],[FebruaryC], [FebruaryM],[MarchC], [MarchM], [AprilC], [AprilM], [MayC], [MayM], [JuneC], [JuneM], [JulyC], [JulyM],
     [AugustC], [AugustM],[SeptemberC] , [SeptemberM],[OctoberC] ,[OctoberM],[NovemberC], [NovemberM], [DecemberC], [DecemberM]

)
)As PivotTable