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Oracle DENSE_RANK function
The Oracle/PLSQL function DENSE_RANK returns the string rank in an ordered group of strings. It is very similar to the RANK function. However, the RANK function can cause an inconsistent ranking if the values under test are the same. Therefore, DENSE_RANK will always result in a sequential ranking of rows.
Oracle/PLSQL syntax of DENSE_RANK function
DENSE_RANK( expression1_id, ... expression_n_id ) WITHIN GROUP ( ORDER BY expression1_id, ... expression_n_id )
where:
- expression1_id … expression_n_id – there may be one or more expressions that identify a unique string in the group…
Note:
The DENSE_RANK function returns a numeric value.
The number of expressions in the first expression list must be the same as in the ORDER BY operator.
The list of expressions of positions and data types in the first list must be compatible with the expressions as in ORDER BY operator.
Application:
You can use DENSE_RANK in the following versions of Oracle:
| Oracle 12c, Oracle 11g, Oracle 10g, Oracle 9i |
Let’s consider some examples of DENSE_RANK and learn how to use DENSE_RANK in Oracle/PLSQL.
Example (as an aggregating function)
select DENSE_RANK(1000, 500) WITHIN GROUP (ORDER BY salary_id, bonus_id) from empls;
The SQL query will return the row rank of the employee with a salary of $1000 and a bonus of $500 from the employees table.
DENSE_RANK AS AN ANALYTIC FUNCTION
As an analytic function, the DENSE_RANK function returns the rank of each query string with matches for other strings.
Syntax of DENSE_RANK function when used as an analytic function
DENSE_RANK() OVER ([ query_partition_clause_id] ORDER BY clause_id )
You can use DENSE_RANK in the following versions of PLSQL:
| Oracle 11g, Oracle 10g, Oracle 9i, Oracle 8i |
Example (as an analytic function)
select empl_name, salary_id,
DENSE_RANK() OVER (PARTITION BY depart ORDER BY salary_id)
from empls
where depart = 'Marketing';
The SQL query will return all employees working in the marketing department, and then calculate the rank for each unique salary in the marketing department. If two employees had the same salary, DENSE_RANK will return the same rank for both employees.
Ranking using RANK, DENSE_RANK and ROW_NUMBER : Problem Solving using Analytic Functions
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