ROW_NUMBER() in MySQL

mysql sql greatest-n-per-group rank row-number

Paul · Dec 13, 2009 · Viewed 550k times · Source

Is there a nice way in MySQL to replicate the SQL Server function ROW_NUMBER()?

For example:

SELECT 
    col1, col2, 
    ROW_NUMBER() OVER (PARTITION BY col1, col2 ORDER BY col3 DESC) AS intRow
FROM Table1

Then I could, for example, add a condition to limit intRow to 1 to get a single row with the highest col3 for each (col1, col2) pair.

Answer

There is no ranking functionality in MySQL. The closest you can get is to use a variable:

SELECT t.*, 
       @rownum := @rownum + 1 AS rank
  FROM YOUR_TABLE t, 
       (SELECT @rownum := 0) r

so how would that work in my case? I'd need two variables, one for each of col1 and col2? Col2 would need resetting somehow when col1 changed..?

Yes. If it were Oracle, you could use the LEAD function to peak at the next value. Thankfully, Quassnoi covers the logic for what you need to implement in MySQL.