Question

I have the following table:

UserID      Sub     EID 
1       TA      1
1       TA      6
1       TA      2
2       TA      7
2       GB      7
3       TA      6
3       TA      1
3       GB      7
3       MX      7
3       MX      6

I am trying to run a sql statement that will transform the “Sub” field by adding a number starting from 1 every time that there is a duplicate for a particular userid. Below is what the table should look like after I apply the statement. I don’t know how this can be accomplished. I am using SQL Server 2008.

UserID      Sub     EID
1       TA1     1
1       TA2     6
1       TA3     2
2       TA1     7
2       GB1     7
3       TA1     6
3       TA2     1
3       GB1     7
3       MX1     7
3       MX2     6

Thanks in advance for your help.

Answer 1

Use ROW_NUMBER()OVER. This example uses a table variable:

DECLARE @t TABLE(UserID INT, Sub VARCHAR(5), EID INT);
INSERT INTO @t VALUES
(1,'TA',1)
, (1,'TA',6)
, (1,'TA',2)
, (2,'TA',7)
, (2,'GB',7)
, (3,'TA',6)
, (3,'TA',1)
, (3,'GB',7)
, (3,'MX',7)
, (3,'MX',6);

SELECT UserID
, Sub=Sub+CAST(ROW_NUMBER()OVER(PARTITION BY UserID, Sub ORDER BY UserID) AS VARCHAR(30))
, EID
FROM @t

Result:

UserID      Sub                                 EID
----------- ----------------------------------- -----------
1           TA1                                 1
1           TA2                                 6
1           TA3                                 2
2           GB1                                 7
2           TA1                                 7
3           GB1                                 7
3           MX1                                 7
3           MX2                                 6
3           TA1                                 6
3           TA2                                 1