SQL in a Nutshell, 3rd Edition

Name

DENSE_RANK

Computes a rank in a group for a hypothetical row that you supply. This is a dense rank, which means rankings are never skipped, even when a group contains rows that rank identically.

ANSI SQL Standard Syntax

DENSE_RANK(value_list) WITHIN GROUP (ORDER BY sort_list)
value_list ::= expression[, expression...]
sort_list ::= sort_item[, sort_item...]
sort_item ::= expression [ASC | DESC] [NULLS FIRST | NULLS LAST]

Items in the value_list correspond by position to items in the sort_list. Therefore, both lists must have the same number of expressions.

Oracle and SQL Server

Oracle and SQL Server follow the ANSI SQL syntax and implement the following analytic syntax:

DENSE_RANK(  ) OVER ([partioning]ordering)

For an explanation of the partioning and order clauses, see the section later in this chapter titled “ANSI SQL Window Functions.”

MySQL and PostgreSQL

These platforms do not implement the DENSE_RANK aggregate function.

Example

The following example determines the dense rank of the hypothetical new row (num=4, odd=1) within each group of rows from test4, where groups are distinguished by the values in the odd column:

SELECT * FROM test4;
       NUM        ODD
---------- ----------
         0          0
         1          1
         2          0
         3          1
         3          1
         4          0
         5          1
SELECT odd, DENSE_RANK(4,1) WITHIN GROUP (ORDER BY num, odd)
FROM test4 GROUP BY odd;
       ODD DENSE_RANK(4,1)WITHINGROUP(ORDERBYNUM,ODD)
---------- ------------------------------------------
         0                                          4
         1                                          3

In the group odd=0, the new row comes after (0,0), (2,0), and (4,0), and thus it is in position 4. ...