VARIANCE

Syntax

Description of the illustration variance.gif

Purpose

VARIANCE returns the variance of expr. You can use it as an aggregate or analytic function.

Oracle Database calculates the variance of expr as follows:

• 0 if the number of rows in expr = 1

• VAR_SAMP if the number of rows in expr > 1

If you specify DISTINCT, then you can specify only the query_partition_clause of the analytic_clause. The order_by_clause and windowing_clause are not allowed.

This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument.

Aggregate Example

The following example calculates the variance of all salaries in the sample employees table:

SELECT VARIANCE(salary) "Variance"
   FROM employees;

  Variance
----------
15283140.5

Analytic Example

The following example returns the cumulative variance of salary values in Department 30 ordered by hire date.

SELECT last_name, salary, VARIANCE(salary) 
      OVER (ORDER BY hire_date) "Variance"
   FROM employees 
   WHERE department_id = 30; 

LAST_NAME           SALARY   Variance
--------------- ---------- ----------
Raphaely             11000          0
Khoo                  3100   31205000
Tobias                2800 21623333.3
Baida                 2900 16283333.3
Himuro                2600   13317000
Colmenares            2500   11307000