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produces what you probably want in this case: +-+-+ might produce this result ( DISTINCT has no effect): +-+-+ĭENSE_RANK() OVER (ORDER BY v) row_number ROW_NUMBER() OVER (ORDER BY v) row_number When you need a generated ROW_NUMBER() on a SELECT DISTINCT statement, the ROW_NUMBER() will produce distinct values before they are removed by the DISTINCT keyword. This article covers an interesting relationship between ROW_NUMBER() and DENSE_RANK() (the RANK() function is not treated specifically). DENSE_RANK also assigns the same rank to all three rows but then the next distinct value is assigned a value of 2. You can see that for the three identical rows the ROW_NUMBER increments, the RANK value remains the same then it leaps to 4. Returns StyleID ID RANK ROW_NUMBER DENSE_RANK ROW_NUMBER() OVER(PARTITION BY StyleID ORDER BY ID) AS ,ĭENSE_RANK() OVER(PARTITION BY StyleID ORDER BY ID) AS RANK() OVER(PARTITION BY StyleID ORDER BY ID) AS , RANK and DENSE_RANK are deterministic in this case, all rows with the same value for both the ordering and partitioning columns will end up with an equal result, whereas ROW_NUMBER will arbitrarily (non deterministically) assign an incrementing result to the tied rows.Įxample: (All rows have the same StyleID so are in the same partition and within that partition the first 3 rows are tied when ordered by ID) WITH T(StyleID, ID) You will only see the difference if you have ties within a partition for a particular ordering value.