VARIANCE

Syntax

Description of variance.gif follows
Description of the illustration variance.gif

See Also:

"Analytic Functions" for information on syntax, semantics, and restrictions

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 data type or any nonnumeric data type that can be implicitly converted to a numeric data type. The function returns the same data type as the numeric data type of the argument.

See Also:

Table 3-10, "Implicit Type Conversion Matrix" for more information on implicit conversion, "About SQL Expressions" for information on valid forms of expr and "Aggregate Functions"

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
   ORDER BY last_name, salary, "Variance"; 

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