sql查詢找到潛在的重複記錄

Question

我正在根據僱主的數據找出重複的僱主根據他們的名字。

的數據是這樣的：

Employer ID | Legal Name | Operating Name 
------------- | ---------------| -------------------- 
1    |  AA  |  AA 
2    |  BB  |  AA 
3    |  CC  |  BB 
4    |  DD  |  DD 
5    |  ZZ  |  ZZ 

現在，如果我試圖找到僱主AA的所有重複的查詢應該返回以下結果：

Employer ID | Legal Name | Operating Name 
------------- | ---------------| -------------------- 
1    |  AA  |  AA 
2    |  BB  |  AA 
3    |  CC  |  BB 

僱主1的法定名稱和單位2的操作名稱是與搜索的直接匹配。 但是，捕獲的是僱主3，它與搜索字符串沒有直接關係，但僱主2的合法名稱與僱主3的工作名稱相匹配。

而我需要的搜索結果達到第n級。我不確定這是否可以通過類似這樣的遞歸查詢來實現。

請幫

我試圖通過遞歸CTE來實現這一點，但後來我意識到，這是進入無限遞歸。下面是代碼：

DECLARE @SearchName VARCHAR(50) 
    SET @SearchName = 'AA' 
    ;With CTE_EmployerNames 
    AS 
    (
-- Anchor Member definition 
select * 
from [dbo].[Name_Table] 
where Leg_Name = @SearchName 
OR  Op_Name = @SearchName 
UNION ALL 
-- Recursive Member definition 
select N.* 
from [dbo].[Name_Table] N 
JOIN CTE_EmployerNames C 
ON  N.ID <> C.ID 
AND  (N.Leg_Name = C.Leg_Name 
OR  N.Leg_Name = C.Op_Name 
OR  N.Op_Name = C.Leg_Name 
OR  N.Op_Name = C.Op_Name) 
    ) 

    select * 
    from CTE_EmployerNames 

更新： 我創建了一個存儲過程來達到我想要的。但是由於循環和遊標，這個過程有點慢。截至目前，這正在解決我的問題，幾乎不影響執行時間。任何建議來優化它或另一種方式來做到這一點將不勝感激。多謝你們。這裏是代碼：

CREATE PROCEDURE [dbo].[Get_Similar_Name_Employers] 
@P_BaseName VARCHAR(100) 
AS 
BEGIN 
DECLARE @ID INT 
DECLARE @Leg_Name VARCHAR(50) 
DECLARE @Op_Name VARCHAR(50) 

-- Create temp table to hold data temporarily 
CREATE TABLE #Temp_Employers 
(
    [ID] [int] NULL, 
    [Leg_Name] [varchar](50) NULL, 
    [Op_Name] [varchar](50) NULL, 
    [Status] [bit] null -- To keep track if that record is processed or not 
) 

-- Insert all records which are directly matching with search criteria 
INSERT INTO #Temp_Employers 
SELECT NT.ID, NT.Leg_Name, NT.Op_Name, 0 
FROM dbo.Name_Table NT 
WHERE NT.Leg_Name = @P_BaseName 
OR  NT.Op_Name = @P_BaseName 

while EXISTS (SELECT 1 from #Temp_Employers where Status = 0) -- until all rows are processed 
BEGIN 
    DECLARE @EmployerCursor CURSOR 
    SET  @EmployerCursor = CURSOR FAST_FORWARD 
    FOR 
      SELECT ID, Leg_Name, Op_Name 
      from #Temp_Employers 
      where Status = 0 

    OPEN @EmployerCursor 

    FETCH NEXT 
    FROM @EmployerCursor 
    INTO @ID, @Leg_Name, @Op_Name 

    WHILE @@FETCH_STATUS = 0 
    BEGIN 
     -- For every unprocessed record in temp table check if there is any possible duplicate. 
     -- and insert all possible duplicate records in same table for further processing to find their possible duplicates  
     INSERT INTO #Temp_Employers 
     select ID, Leg_Name, Op_Name, 0 
     from dbo.Name_Table 
     WHERE (Leg_Name = @Leg_Name 
     OR  Op_Name = @Op_Name 
     OR  Leg_Name = @Op_Name 
     OR  Op_Name = @Leg_Name) 
     AND  ID NOT IN (select ID 
          FROM #Temp_Employers) 

     -- Update status of recently processed record to avoid processing again 
     UPDATE #Temp_Employers 
     SET  Status = 1 
     WHERE ID = @ID 

     FETCH NEXT 
     FROM @EmployerCursor 
     INTO @ID, @Leg_Name, @Op_Name 
    END 

    -- close cursor and deallocate memory 
    CLOSE @EmployerCursor 
    DEALLOCATE @EmployerCursor 
END 

select ID, 
     Leg_Name, 
     Op_Name 
from #Temp_Employers 
Order By ID 

DROP TABLE #Temp_Employers 

END 

Answer 1

你可以用兩個自連接來完成這個。我以前DISTINCT是安全的 - 你不需要它你的榜樣，但可能會爲您的實際數據：只要你喜歡

SELECT DISTINCT T2.EMPID, T2.LEGAL_NAME, T.LEGAL_NAME 
FROM TABLE T 
INNER JOIN TABLE T2 ON T.LEGAL_NAME = T2.OPERATING_NAME 
INNER JOIN TABLE T3 ON T2.OPERATING_NAME = T3.OPERATING_NAME 
WHERE T.LEGAL_NAME <> T3.LEGAL_NAME 

重命名和別名表和列。

SQL Fiddle Example

編輯 - 如果你也想記錄中，其中OP名字是從法律的名稱簡直是天壤之別，UNION那些：

SELECT DISTINCT T2.EMPID, T2.LEGAL_NAME, T.LEGAL_NAME 
FROM TABLE T 
INNER JOIN TABLE T2 ON T.LEGAL_NAME = T2.OPERATING_NAME 
INNER JOIN TABLE T3 ON T2.OPERATING_NAME = T3.OPERATING_NAME 
WHERE T.LEGAL_NAME <> T3.LEGAL_NAME 

UNION 

SELECT EMPID, LEGAL_NAME, OP_NAME 
FROM TABLE 
WHERE LEGAL_NAME <> OP_NAME 

SQL Fiddle Example 2

Answer 2

你基本上是試圖要創建一個directed acyclic graph，其中節點是名稱，並且您想要查找通向您的員工的所有名稱。

有一個在Oracle Tip: Solving directed graph problems with SQL, part 1一開始教程，並在Directed graph SQL一個相關的StackOverflow問題。