的SQL Server 2005 - 。嵌套遞歸查詢:(

Question

我有一個查詢，我需要執行，我不知道如何構建

我有一個表叫員工我有一個名爲公司另一個表有第三個名爲Files的表格，你可以想象，公司有員工，員工有文件

我需要列出我的數據庫中的所有僱員，挑戰是，我需要列出總數在同一家公司的員工檔案我曾嘗試在沒有任何運氣以下變化：

SELECT 
    e.FirstName, 
    e.LastName, 
    e.Company, 
    (SELECT COUNT(*) FROM Files f WHERE f.EmployeeID IN (SELECT [ID] FROM Employees e2 WHERE e2.CompanyID=e.CompanyID)) as 'FileCount' 
FROM 
    Employees e 

我做錯了什麼？謝謝！

Answer 1

試試這個：

SELECT 
    e.FirstName, 
    e.LastName, 
    e.Company, 
    (
    SELECT COUNT(*) 
    FROM Files f 
    JOIN Employees e2 ON f.EmployeeID = e2.id 
    WHERE e2.CompanyID = e.CompanyID 
) as 'FileCount' 
FROM 
    Employees e 

Answer 2

如何：

SELECT 
    e.FirstName, 
    e.LastName, 
    e.Company, 
    select count(*) from Files f, Employees e where f.EmployeeID=e.EmployeeID and e.CompanyID=emp.CompanyID 
FROM 
    Employees emp 

Answer 3

在SELECT子句不相關的解決方案。可能更快......

SELECT 
    e.FirstName, 
    e.LastName, 
    e.Company, 
    foo.FileCount 
FROM 
    Employees e 
    JOIN 
    (
    SELECT 
     COUNT(*) AS FileCount, --OR COUNT(DISTINCT something) ? 
     e2.Company, f.EmployeeID 
    FROM 
     Files f JOIN Employees e2 ON f.EmployeeID = e2.id 
    GROUP BY 
     e2.Company, f.EmployeeID 
    ) foo ON e.Company = foo.Company AND e.id = foo.EmployeeID 

Answer 4

有很多方法可以得到這個。如果性能是一個問題，根據估計的執行計劃成本，這是更優化的。

SELECT 
    e.FirstName, 
    e.LastName, 
    e.Company, 
    COUNT(f.FileId) 
FROM 
    Employees e 
    INNER JOIN Files f ON e.EmployeeID = f.EmployeeID 
GROUP BY 
    e.FirstName, 
    e.LastName, 
    e.Company 

Answer 5

WITH FilesPerCompany (CompanyID, NumberOfFiles) 
AS (SELECT  c.ID AS CompanyID, 
       COUNT(*) AS NumberOfFiles 
    FROM  Companies c 
    INNER JOIN Employees e ON c.ID = e.CompanyID 
    INNER JOIN Files f  ON e.ID = f.EmployeeID 
    GROUP BY c.ID 
) 

SELECT  e.FirstName, 
      e.LastName, 
      e.Company, 
      COALESCE(s.NumberOfFiles, 0) AS NumberOfFilesPerCompany 
FROM  Employees e 
LEFT JOIN FilesPerCompany s 
     ON s.CompanyID = e.CompanyID 

Answer 6

以下語句使用遞歸加入到循環下來誰管理誰管理其他員工的其他員工的員工....等我們的結構是一個有點令人費解的管理結構是基於角色實際上允許一名員工擁有1名以上的經理。您可以在此遞歸中添加對文件的引用。

WITH Manager as 
(SELECT c.Forenames + ' ' + c.Surname as Employee, 
    c2.Forenames + ' ' + c2.Surname AS Manages, 
    c.accountid AS AccountID, c.[Status] AS [Status] 
    FROM [intranet].[dbo].[tblContact] c 
    LEFT JOIN tblContactPost cp ON cp.contactid = c.contactid 
    LEFT JOIN tblPost p ON p.ParentRoleId = cp.RoleID AND p.ParentPostArea = cp.PostArea AND p.ParentPostNo = cp.PostNo 
    INNER JOIN tblContactPost cp2 ON cp2.RoleId = p.RoleId AND cp2.PostArea = p.PostArea AND cp2.PostNo = p.PostNo 
    INNER JOIN tblContact c2 ON c2.ContactID = cp2.ContactId 
) 
    ,jn AS 
    (SELECT Employee, Manages 
    FROM Manager 
    Where AccountID = 'ad\lgardner' AND [Status] = 'A' 
    UNION ALL 
    SELECT c.Employee, c.Manages 
    FROM jn as p JOIN Manager AS c 
    ON c.Employee = p.Manages 
    ) 
SELECT jn.Employee, jn.Manages 
From jn 
Order BY 1