ROW_NUMBER window function - Amazon Redshift
SyntaxArgumentsReturn typeExamples

ROW_NUMBER window function

Assigns an ordinal number of the current row within a group of rows, counting from 1, based on the ORDER BY expression in the OVER clause. If the optional PARTITION BY clause is present, the ordinal numbers are reset for each group of rows. Rows with equal values for the ORDER BY expressions receive the different row numbers nondeterministically.

Syntax

ROW_NUMBER() OVER(
  [ PARTITION BY expr_list ]
  [ ORDER BY order_list ]
)

Arguments

( )

The function takes no arguments, but the empty parentheses are required.

OVER

The window function clause for the ROW_NUMBER function.

PARTITION BY expr_list

Optional. One or more column expressions that divide the results into sets of rows.

ORDER BY order_list

Optional. One or more column expressions that defines the order of rows within a set. If no PARTITION BY is specified, ORDER BY uses the entire table.

If ORDER BY does not produce a unique ordering or is omitted, the order of the rows is nondeterministic. For more information, see Unique ordering of data for window functions.

Return type

BIGINT

Examples

The following examples use the WINSALES table. For a description of the WINSALES table, see Sample table for window function examples.

The following example orders the table by QTY (in ascending order), then assigns a row number to each row. The results are sorted after the window function results are applied. 

SELECT salesid, sellerid, qty, 
ROW_NUMBER() OVER(
   ORDER BY qty ASC) AS row
FROM winsales
ORDER BY 4,1;

salesid   sellerid   qty   row
---------+----------+-----+-----
   30001 |        3 |  10 |   1	
   10001 |        1 |  10 |   2	
   10006 |        1 |  10 |   3
   40005 |        4 |  10 |   4
   30003 |        3 |  15 |   5
   20001 |        2 |  20 |   6
   20002 |        2 |  20 |   7
   30004 |        3 |  20 |   8
   10005 |        1 |  30 |   9
   30007 |        3 |  30 |  10
   40001 |        4 |  40 |  11

The following example partitions the table by SELLERID and orders each partition by QTY (in ascending order), then assigns a row number to each row. The results are sorted after the window function results are applied. 

SELECT salesid, sellerid, qty, 
ROW_NUMBER() OVER(
  PARTITION BY sellerid
  ORDER BY qty ASC) AS row_by_seller
FROM winsales
ORDER BY 2,4;

 salesid | sellerid | qty | row_by_seller
---------+----------+-----+-----
   10001 |        1 |  10 |   1
   10006 |        1 |  10 |   2
   10005 |        1 |  30 |   3
   20001 |        2 |  20 |   1
   20002 |        2 |  20 |   2
   30001 |        3 |  10 |   1
   30003 |        3 |  15 |   2
   30004 |        3 |  20 |   3
   30007 |        3 |  30 |   4
   40005 |        4 |  10 |   1
   40001 |        4 |  40 |   2

The following example shows the results when not using the optional clauses. 

SELECT salesid, sellerid, qty, ROW_NUMBER() OVER() AS row
FROM winsales
ORDER BY 4,1;

salesid   sellerid   qty   row
---------+----------+-----+-----
   30001 |        3 |  10 |   1	
   10001 |        1 |  10 |   2	
   10005 |        1 |  30 |   3
   40001 |        4 |  40 |   4
   10006 |        1 |  10 |   5
   20001 |        2 |  20 |   6
   40005 |        4 |  10 |   7
   20002 |        2 |  20 |   8
   30003 |        3 |  15 |   9
   30004 |        3 |  20 |  10
   30007 |        3 |  30 |  11