在 sql server 中使用 partition 和 rank() 删除重复记录时遇到问题

Question

我正在尝试识别重复记录，然后使用 PARTITION 和 RANK() n SQL Server 2008 删除其中一条重复记录。我删除重复记录的条件是它不应在另一个表中引用。

我有一个包含一些重复语言的语言表。员工表有员工和语言映射。如果该语言 ID 未映射到 Employee 表中，我必须删除其中一条重复记录。

CREATE TABLE MY_LANGUAGE (LANGUAGEID INT, LANGUAGENAME VARCHAR(20))
CREATE TABLE MY_EMPLOYEE (EMPID INT, NAME VARCHAR(20), LANGUAGEID INT)

INSERT INTO MY_LANGUAGE VALUES(1, 'ENGLISH')
INSERT INTO MY_LANGUAGE VALUES(2, 'FRENCH')
INSERT INTO MY_LANGUAGE VALUES(3, 'ITALIAN')
INSERT INTO MY_LANGUAGE VALUES(4, 'GERMAN')
INSERT INTO MY_LANGUAGE VALUES(5, 'ITALIAN')
INSERT INTO MY_LANGUAGE VALUES(6, 'GERMAN')
INSERT INTO MY_LANGUAGE VALUES(7, 'SPANISH')

INSERT INTO MY_EMPLOYEE VALUES (10, 'GLEN', 1)
INSERT INTO MY_EMPLOYEE VALUES (20, 'PETER', 2)
INSERT INTO MY_EMPLOYEE VALUES (30, 'MARIA', 3)

如果您看到，我有两种语言是重复的，其中一种正在被员工使用。我想删除语言 ID 4 和 5。

LANGUAGENAME    LANGUAGEID  EMPNAME
GERMAN          4   
GERMAN          6   
ITALIAN             3               MARIA   
ITALIAN             5   

我试图创建一个选择语句来返回我要删除的内容：

WITH CTE AS (
SELECT  L.LANGUAGENAME,  L.LANGUAGEID, RANK() OVER(PARTITION BY L.LANGUAGENAME ORDER BY L.LANGUAGEID) AS RANKING
FROM MY_LANGUAGE L
INNER JOIN (
    SELECT LANGUAGENAME, COUNT(*) AS DUPECOUNT
    FROM MY_LANGUAGE
    GROUP BY LANGUAGENAME
    HAVING COUNT(*) > 1
) LC ON L.LANGUAGENAME = LC.LANGUAGENAME
WHERE NOT EXISTS (SELECT 1 FROM MY_EMPLOYEE WHERE MY_EMPLOYEE.LANGUAGEID = L.LANGUAGEID))  
SELECT * FROM CTE WHERE RANKING = 1

这会返回以下内容

LANGUAGENAME    LANGUAGEID  RANKING
GERMAN              4           1
ITALIAN         5           1

当我尝试删除时出现错误：

WITH CTE AS (
SELECT  L.LANGUAGENAME,  L.LANGUAGEID, RANK() OVER(PARTITION BY L.LANGUAGENAME ORDER BY L.LANGUAGEID) AS RANKING
FROM MY_LANGUAGE L
INNER JOIN (
    SELECT LANGUAGENAME, COUNT(*) AS DUPECOUNT
    FROM MY_LANGUAGE
    GROUP BY LANGUAGENAME
    HAVING COUNT(*) > 1
) LC ON L.LANGUAGENAME = LC.LANGUAGENAME
WHERE NOT EXISTS (SELECT 1 FROM MY_EMPLOYEE WHERE MY_EMPLOYEE.LANGUAGEID = L.LANGUAGEID))  
DELETE FROM CTE WHERE RANKING = 1

我得到的错误是：

消息 4405，第 16 级，状态 1，第 1 行
视图或函数“CTE”不可更新，因为修改会影响多个基表。

任何如何解决这个问题的想法，或者可能是它可以被简化。感谢@Szymon 展示了一个临时表解决方案，但我希望得到一个没有临时表的解决方案（如果可能的话）。

Answer 1

查询：

DELETE ll
FROM MY_LANGUAGE ll
JOIN (SELECT L.LANGUAGENAME,
       L.LANGUAGEID,
       ROW_NUMBER()OVER(PARTITION BY L.LANGUAGENAME, e.EMPID
                        ORDER BY L.LANGUAGEID ASC) rnk,
       COUNT(*)OVER(PARTITION BY L.LANGUAGENAME) cnt,
       e.EMPID
      FROM MY_LANGUAGE l
      LEFT JOIN MY_EMPLOYEE e ON e.LANGUAGEID = l.LANGUAGEID)  a 
    ON ll.LANGUAGEID = a.LANGUAGEID
AND a.rnk = 1
AND a.cnt > 1
and a.EMPID IS NULL

结果：

| LANGUAGEID | LANGUAGENAME |
|------------|--------------|
|          1 |      ENGLISH |
|          2 |       FRENCH |
|          3 |      ITALIAN |
|          6 |       GERMAN |
|          7 |      SPANISH |

Answer 2

您可以将 CTE 查询中的记录放入临时表中，然后根据该表删除。

WITH CTE AS (
SELECT  L.LANGUAGENAME,  L.LANGUAGEID, RANK() OVER(PARTITION BY L.LANGUAGENAME ORDER BY L.LANGUAGEID) AS RANKING
FROM MY_LANGUAGE L
INNER JOIN (
    SELECT LANGUAGENAME, COUNT(*) AS DUPECOUNT
    FROM MY_LANGUAGE
    GROUP BY LANGUAGENAME
    HAVING COUNT(*) > 1
) LC ON L.LANGUAGENAME = LC.LANGUAGENAME
WHERE NOT EXISTS (SELECT 1 FROM MY_EMPLOYEE WHERE MY_EMPLOYEE.LANGUAGEID = L.LANGUAGEID))  
SELECT * INTO #temp FROM CTE WHERE RANKING = 1

然后使用#temp中的记录从原表中删除。

Answer 3

试试这个..

;WITH CTE AS (
SELECT t.LANGUAGEID, LANGUAGENAME, RANK() OVER(PARTITION BY T.LANGUAGENAME ORDER BY T.LANGUAGEID) AS RANKING
FROM MY_LANGUAGE T 
WHERE T.LANGUAGEID  IN (
                        SELECT  L.LANGUAGEID 
                        FROM MY_LANGUAGE L LEFT JOIN MY_EMPLOYEE E
                        ON L.LANGUAGEID = E.LANGUAGEID
                        WHERE E.LANGUAGEID IS NULL)
) 
DELETE FROM CTE
WHERE RANKING = 1 AND (CTE.LANGUAGENAME IN (SELECT LANGUAGENAME 
                                        FROM MY_LANGUAGE 
                                        GROUP BY LANGUAGENAME
                                        HAVING COUNT(LANGUAGENAME) > 1))