刪除重複的行？

Question

我想根據類別ID從我的表中刪除重複的行，但不希望全部刪除，如果有多個具有相同類別ID的行，我想留下一行。

這是我的查詢我讓我需要改變它。

delete from twinhead_tblcategory where categoryid in (select categoryid from twinhead_tblcategory group by categoryid having count(categoryid) > 1) 

Answer 1

對於SQL Server，你可以做到這一點：

WITH MyTableCTE (CategoryId, RowNumber) 
AS 
(
    SELECT CategoryId, ROW_NUMBER() OVER (ORDER BY CategoryId) AS 'RowNumber' 
    FROM MyTable 

) 

Delete From MyTableCTE Where RowNumber > 1 

Answer 2

做一個select distinct到一個新表，刪除舊，並重新命名新一成舊錶名。

Answer 3

在這裏檢查sql服務器 - http://support.microsoft.com/kb/139444 - 這應該讓你開始。

Answer 4

這可能是笨手笨腳的，但也許你可以選擇不同的*到臨時表中，然後截斷表，然後在表中插入臨時表的內容。不過，外鍵約束可能會阻止這一點。

Answer 5

如果行有一個獨特的id列，那麼這應該工作：

DELETE t1 FROM your_table t1, your_table t2 
WHERE t1.column1 = t2.column1 AND t1.column2 = t2.column2 
AND ... /* check equality of all relevant columns */ 
AND t1.id < t2.id 

Answer 6

使用Sql Server，你可以通過全項，通過的categoryID下令使用遊標循環。

當前的ID是否與上一個相同？然後刪除它，參見this article的示例C. 否則請記住下一輪的ID。

Answer 7

您有刪除duplicate rows幾種方式。

我的解決方案，首先考慮該表例如

CREATE TABLE #Employee 
(
ID   INT, 
FIRST_NAME NVARCHAR(100), 
LAST_NAME NVARCHAR(300) 
) 

INSERT INTO #Employee VALUES (1, 'Vahid', 'Nasiri'); 
INSERT INTO #Employee VALUES (2, 'name1', 'lname1'); 
INSERT INTO #Employee VALUES (3, 'name2', 'lname2'); 
INSERT INTO #Employee VALUES (2, 'name1', 'lname1'); 
INSERT INTO #Employee VALUES (3, 'name2', 'lname2'); 
INSERT INTO #Employee VALUES (4, 'name3', 'lname3'); 

首先解決方法：使用另一臺用於重複行。

SELECT DISTINCT * 
FROM #Employee 

SELECT * INTO #DuplicateEmployee 
FROM #Employee 

INSERT #DuplicateEmployee 
SELECT DISTINCT * 
FROM #Employee 

BEGIN TRAN 
DELETE #Employee 
INSERT #Employee 
SELECT * 
FROM #DuplicateEmployee 

COMMIT TRAN 

DROP TABLE #DuplicateEmployee 

SELECT DISTINCT * 
FROM #Employee 

解決方法二：

SELECT DISTINCT * FROM #Employee 

SELECT * INTO #DuplicateEmployee FROM #Employee 

INSERT #DuplicateEmployee 
SELECT ID, 
    FIRST_NAME, 
    LAST_NAME 
FROM #Employee 
GROUP BY 
    ID,FIRST_NAME,LAST_NAME 
HAVING COUNT(*) > 1 

BEGIN TRAN 
DELETE #Employee 
FROM #DuplicateEmployee 
WHERE #Employee.ID = #DuplicateEmployee.ID 
AND #Employee.FIRST_NAME = #DuplicateEmployee.FIRST_NAME 
AND #Employee.LAST_NAME = #DuplicateEmployee.LAST_NAME 

INSERT #Employee 
SELECT * 
FROM #DuplicateEmployee 

COMMIT TRAN 
DROP TABLE #DuplicateEmployee 

SELECT DISTINCT * FROM #Employee 

滿含淚水的解決方案：使用rowcount

SELECT DISTINCT * 
FROM #Employee 

SET ROWCOUNT 1 
SELECT 1 
WHILE @@rowcount > 0 
    DELETE #Employee 
    WHERE 1 < (
      SELECT COUNT(*) 
      FROM #Employee a2 
      WHERE #Employee.ID = a2.ID 
       AND #Employee.FIRST_NAME = a2.FIRST_NAME 
       AND #Employee.LAST_NAME = a2.LAST_NAME 
    ) 

SET ROWCOUNT 0 

SELECT DISTINCT * 
FROM #Employee 

方案四：使用Analytical Functions

SELECT DISTINCT * 
FROM #Employee; 

WITH #DeleteEmployee AS (
        SELECT ROW_NUMBER() 
          OVER(PARTITION BY ID, First_Name, Last_Name ORDER BY ID) AS 
          RNUM 
        FROM #Employee 
       ) 

DELETE 
FROM #DeleteEmployee 
WHERE RNUM > 1 

SELECT DISTINCT * 
FROM #Employee 

第五的解決方案：使用identity場

SELECT DISTINCT * 
FROM #Employee; 

ALTER TABLE #Employee ADD UNIQ_ID INT IDENTITY(1, 1) 

DELETE 
FROM #Employee 
WHERE UNIQ_ID < (
    SELECT MAX(UNIQ_ID) 
    FROM #Employee a2 
    WHERE #Employee.ID = a2.ID 
      AND #Employee.FIRST_NAME = a2.FIRST_NAME 
      AND #Employee.LAST_NAME = a2.LAST_NAME 
) 

ALTER TABLE #Employee DROP COLUMN UNIQ_ID 

SELECT DISTINCT * 
FROM #Employee 

，所有解決方案的最終使用此命令

DROP TABLE #Employee 

來源我的回答是this site