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Overview

The RANK() window function determines the rank of a value in a group of values, based on the ORDER BY expression in the OVER clause. It can be used with all data types supported by Oxla.

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Syntax

The syntax for this function is as follows: 
RANK() OVER (
    [PARTITION BY partition_expression, ... ]
    ORDER BY sort_expression [ASC | DESC], ...
)
Rows with equal values for the ranking criteria receive the same rank. The output type for this function is BIGINT and it indicates the rank of values in a table, regardles of the input types.
  • If the optional PARTITION BY expression is present, the rankings are reset for each group of rows
  • If the ORDER BY expression is omitted then all ranks are equal to 1

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Parameters

  • (): this function takes no arguments but parentheses is required

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Examples

For the needs of this section, we will create the winsales table that stores details about some sales transactions: 
CREATE TABLE winsales(
    salesid int,
    dateid date,
    sellerid int,
    buyerid text,
    qty int,
    qty_shipped int);
INSERT INTO winsales VALUES
    (30001, '8/2/2003', 3, 'b', 10, 10),
    (10001, '12/24/2003', 1, 'c', 10, 10),
    (10005, '12/24/2003', 1, 'a', 30, null),
    (40001, '1/9/2004', 4, 'a', 40, null),
    (10006, '1/18/2004', 1, 'c', 10, null),
    (20001, '2/12/2004', 2, 'b', 20, 20),
    (40005, '2/12/2004', 4, 'a', 10, 10),
    (20002, '2/16/2004', 2, 'c', 20, 20),
    (30003, '4/18/2004', 3, 'b', 15, null),
    (30004, '4/18/2004', 3, 'b', 20, null),
    (30007, '9/7/2004', 3, 'c', 30, null);

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RANK() with ORDER BY

In this example, we will focus on executing the RANK() function with ORDER BY keyword and calculate the rank of all rows based on the quantity sold: 
SELECT salesid, qty
    RANK() OVER (ORDER BY qty)
FROM winsales
ORDER BY 2,1;
Here is the output for the query presented above that includes the sales ID along with the quantity sold and regular ranks: 
 salesid | qty | rank 
---------+-----+------
   10001 |  10 |    1
   10006 |  10 |    1
   30001 |  10 |    1
   40005 |  10 |    1
   30003 |  15 |    5
   20001 |  20 |    6
   20002 |  20 |    6
   30004 |  20 |    6
   10005 |  30 |    9
   30007 |  30 |    9
   40001 |  40 |   11
(11 rows)

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RANK() with ORDER BY and PARTITION BY

In this example, we will focus on executing the RANK() function with ORDER BY keyword and PARTITION BY clause, partition the table by seller ID, order each partition by the quantity and assign a rank to each row: 
SELECT salesid, sellerid, qty
    RANK() OVER (PARTITION BY sellerid ORDER BY qty)
FROM winsales
ORDER BY 2,3,1;
Here is the output for the query presented above: 
 salesid | sellerid | qty | rank 
---------+----------+-----+------
   10001 |        1 |  10 |    1
   10006 |        1 |  10 |    1
   10005 |        1 |  30 |    3
   20001 |        2 |  20 |    1
   20002 |        2 |  20 |    1
   30001 |        3 |  10 |    1
   30003 |        3 |  15 |    2
   30004 |        3 |  20 |    3
   30007 |        3 |  30 |    4
   40005 |        4 |  10 |    1
   40001 |        4 |  40 |    2
(11 rows)