Question

If I have a table where the cells in a column should not have the same values, how do I check this and update? (I know I can set constraints in the settings, but I don’t want to do that.)

Say the column name is called unique hash name and contains

 Peter Peter Peter Dave Dave 

and so on. I want that to transform to:

 Peter Peter1 Peter2 Dave Dave1 

What is the T-SQL for SQL Server to do that?

Update: For clarity’s sake, let’s call the table ‘Persons’ and the cell I want unique ‘UniqueName’. Could you make it a SELECT-statement, so I can test the result before updating. And I am using SQL Server 2005 and above.

Answer 1

EDIT: I’ve changed the query to use your field names and added a ‘select-only’ query for you to preview.

This is actually pretty easy to do… just use ROW_NUMBER() with a PARTITION clause:

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 

If you want a ‘select-only’, then here you go:

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 

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EDIT Again: If you’re looking for a SQL Server 2000 Solution…

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