删除重复行？

Question

我想根据类别 ID 从我的表中删除重复的行，但不想全部删除，如果有多个具有相同类别 ID 的行，我想留下一行。

这是我的查询，我需要更改它。

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

Answer 1

对于 SQL Server，您可以这样做：

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

在新表中做一个select distinct，删除旧表并将新表重命名为旧表名。

Answer 3

如果您的行有一个不同的 id 列，那么这应该可以：

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 4

在此处查看 sql server - http://support.microsoft.com/kb/139444 - 这应该可以帮助您入门。

Answer 5

这可能是笨拙的，但也许您可以在临时表中选择 distinct *，然后截断该表，然后将临时表的内容插入表中。不过，外键约束可能会阻止这种情况。

Answer 6

对于 SqlServer，您可以使用游标遍历所有项目，按该 categoryID 排序。

当前的ID和之前的ID一样吗？然后删除它，参见this article 的示例 C。 否则请记住下一轮的 ID。

Answer 7

你有几种删除duplicate rows的方法。

对于我的解决方案，首先以这张表为例

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' );

第一个解决方案：为重复行使用另一个表。

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 

第二种解决方案：

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

撕裂的解决方案：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

第四个解决方案：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

第五个解决方案：使用identity字段

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

所有解决方案的结尾都使用此命令

DROP TABLE #Employee

我的答案来源是this site