SQL in a Nutshell, 2nd Edition

Name

DENSE_RANK

Synopsis

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

SQL2003 Syntax

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

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]

Oracle

Oracle follows the SQL2003 syntax and implements 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 Section 4.3.

DB2, MySQL, PostgreSQl, and SQL Server

These platforms do not implement the DENSE_RANK aggregate function. However, DB2 does support DENSE_RANK as an analytic function. See the section later in this chapter titled Section 4.3.

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 ...