How to return a incremental group number per group in SQL

Question

I would like create a data query in SQL to incrementally number groups of rows, grouped on a common datetime and keep the \"group numbers\" incrementing on the next datetime

Answer 1

you shouldn't be using ROW_NUMBER(),

• use DENSE_RANK() instead
• remove PARTITION BY

query,

SELECT hl.ts_DateTime,  
       hl.Tagname as [ID],  
       hl.TagValue as [Value],
       DENSE_RANK() OVER (ORDER BY ts_datetime) AS RowFilter
FROM   Table1 hl 
ORDER  BY RowFilter

• SQLFiddle Demo

Answer 2

I think you are looking for this:

ROW_NUMBER() OVER (PARTITION BY hl.id ORDER BY hl.ts_DateTime) AS RowFilter