的SQL Server 2005 - 。嵌套递归查询:(

Question

我有一个查询，我需要执行，我不知道如何构建

我有一个表叫员工我有一个名为公司另一个表有第三个名为Files的表格，你可以想象，公司有员工，员工有文件

我需要列出我的数据库中的所有雇员，挑战是，我需要列出总数在同一家公司的员工档案我曾尝试在没有任何运气以下变化：

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 

我做错了什么？谢谢！

Answer 1

试试这个：

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子句不相关的解决方案。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这个。如果性能是一个问题，根据估计的执行计划成本，这是更优化的。

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

以下语句使用递归加入到循环下来谁管理谁管理其他员工的其他员工的员工....等我们的结构是一个有点令人费解的管理结构是基于角色实际上允许一名员工拥有1名以上的经理。您可以在此递归中添加对文件的引用。

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