T-SQL:如何使单元格值独一无二？

Question

如果我有一个表格,其中列中的单元格不应具有相同的值,我该如何检查并更新？(我知道我可以在设置中设置约束,但我不想这样做.)

假设列名称称为唯一哈希名称并包含

Peter
Peter
Peter
Dave
Dave

等等.我想要转换为:

Peter
Peter1
Peter2
Dave
Dave1

SQL Server的T-SQL是做什么的？

更新:为了清楚起见,让我们调用表"Persons"和我想要唯一的单元"UniqueName".你能把它作为SELECT语句,所以我可以在更新之前测试结果.我正在使用SQL Server 2005及更高版本.

Answer 1

编辑:我已更改查询以使用您的字段名称并添加"仅选择"查询供您预览.

这实际上很容易...只需使用带有PARTITION子句的ROW_NUMBER():

UPDATE Persons SET UniqueName = temp.DeDupded FROM
    (SELECT ID,
        CASE WHEN ROW_NUMBER() OVER
            (PARTITION BY UniqueName ORDER BY UniqueName) = 1 THEN UniqueName
        ELSE UniqueName + CONVERT(VARCHAR, ROW_NUMBER()
            OVER (PARTITION BY UniqueName ORDER BY UniqueName)-1) END AS DeDupded
    FROM Persons) temp
WHERE Persons.ID = temp.ID

如果您想要"仅限选择",那么请转到:

SELECT ID,
    CASE WHEN ROW_NUMBER() OVER
        (PARTITION BY UniqueName ORDER BY UniqueName) = 1 THEN UniqueName
    ELSE UniqueName + CONVERT(VARCHAR, ROW_NUMBER()
        OVER (PARTITION BY UniqueName ORDER BY UniqueName)-1) END AS DeDupded
FROM Persons

再次编辑:如果您正在寻找SQL Server 2000解决方案......

CREATE TABLE #Persons ( ID INT IDENTITY(1, 1), UniqueName VARCHAR(100) )

INSERT INTO #Persons VALUES ('Bob')
INSERT INTO #Persons VALUES ('Bob')
INSERT INTO #Persons VALUES ('Bob')
INSERT INTO #Persons VALUES ('John')
INSERT INTO #Persons VALUES ('John')

SELECT
    ID,
    CASE WHEN Position = 0 THEN UniqueName
        ELSE UniqueName + (CONVERT(VARCHAR, Position))
    END AS UniqueName
FROM
    (SELECT
        ID,
        UniqueName,
        (SELECT COUNT(*) FROM #Persons p2 WHERE
            p1.UniqueName = p2.UniqueName AND p1.ID > p2.ID) AS Position
    FROM
        #Persons p1) _temp

DROP TABLE #Persons