如何避免递归CTE重复定位值

Question

我正在使用以下CTE来获取经理和员工的层次结构，我有一个员工的多个经理，在这种情况下，我不希望CTE重复为该员工一次又一次因为它是做在我的代码 - getemp()是一个简单的函数返回employeeid, name and managerID

;With hierarchy as 
(
select [Level]=1 , * from dbo.getemp() where managerid = 1 
union all 
select [Level]+1 , e.* from getemp() e 
join hierarchy h on h.employeeid = e.managerid 

) 
Select * from hierarchy 

编辑后 - 以下办法为我工作。 CTE有可能吗？

SET NOCOUNT ON; 
    DECLARE @Rows int 


    SELECT [Level] = ISNULL(1,0), 
     employeeid = ISNULL(employeeid, 0), 
     empname = CAST(empname as varchar(10)), 
     managerid = ISNULL(managerid,0) 
     into #Temp1 
     from dbo.getemp() as a1 
     where a1.managerid = @Top1 
     --select * from #Temp1 
     SELECT @Rows=@@ROWCOUNT 

     DECLARE @I INT = 2; 
     while @Rows > 0 
     BEGIN 

    Insert into #Temp1 
    select @I as Level, b.employeeid, b.empname, b.managerid from #Temp1 as e 
    inner join (select [employeeid], [empname], [managerid] from dbo.GetEmp())  as b on b.managerid = e.employeeid 
    where e.Level = @I - 1 
    and not exists (
    SELECT 1 FROM #Temp1 t 
    WHERE b.employeeid = t.employeeid 
    AND b.managerid = t.managerid); 
    SELECT @Rows=@@ROWCOUNT 
    --SELECT @Rows AS Rows 
    IF @Rows > 0 
    BEGIN 
    SELECT @I = @I + 1; 
    END 


END 

select distinct * from #Temp1 
END 

Answer 1

无法找到使用CTE的解决方案，所以我用了while循环，以避免重复锚，这里的代码..

DECLARE @Rows int 
    SELECT [Level] = ISNULL(1,0), 
     employeeid = ISNULL(employeeid, 0), 
     empname = CAST(empname as varchar(10)), 
     managerid = ISNULL(managerid,0) 
     into #Temp1 
     from dbo.getemp() as a1 
     where a1.managerid = @Top1 
     --select * from #Temp1 
     SELECT @Rows=@@ROWCOUNT 

     DECLARE @I INT = 2; 
     while @Rows > 0 
     BEGIN 

    Insert into #Temp1 
    select @I as Level, b.employeeid, b.empname, b.managerid from #Temp1 as e 
    inner join (select [employeeid], [empname], [managerid] from dbo.GetEmp())  as b on b.managerid = e.employeeid 
    where e.Level = @I - 1 
    and not exists (
    SELECT 1 FROM #Temp1 t 
    WHERE b.employeeid = t.employeeid 
    AND b.managerid = t.managerid); 
    SELECT @Rows=@@ROWCOUNT 
    --SELECT @Rows AS Rows 
    IF @Rows > 0 
    BEGIN 
    SELECT @I = @I + 1; 
    END 
END 
select distinct * from #Temp1 
END 

Answer 2

既然你有几个管理人员，这意味着人们也可以在几个不同的层次，由于在经理有不同的等级，你可以只需要为每个分支的最低水平像这样的东西：

;With hierarchy as 
(
    select [Level]=1 , * from dbo.getemp() where managerid = 1 
    union all 
    select [Level]+1 , e.* from getemp() e 
    join hierarchy h on h.employeeid = e.managerid 
) 

Select min(Level) as Level, employeeid, name, managerid from hierarchy 
group by employeeid, name, managerid 

使用函数在每次递归中返回所有员工可能不是关于性能的最佳解决方案，尤其是如果它不是内联函数。您可能想考虑使用例如临时。表，如果你不能直接读取表。