ASA SQL Reference
SQL Functions
Alphabetical list of functions
Computes the statistical variance of a population consisting of a numeric-expression, as a DOUBLE.
VAR_POP ( numeric-expression )
numeric-expression The expression whose population-based variance is calculated over a set of rows. The expression is commonly a column name.
The population-based variance (s2) is computed according to the following formula:
s2 = (1/N) * SUM( xi - mean( x ) )2
This variance does not include rows where numeric-expression is NULL. It returns NULL for a group containing no rows.
SQL/92 Vendor extension.
SQL/99 SQL/foundation feature outside of core SQL.
Sybase Not supported by Adaptive Server Enterprise.
The following statement lists the average and variance in the number of items per order in different time periods:
SELECT year( ship_date ) AS Year, quarter( ship_date ) AS Quarter, avg( quantity ) AS Average, var_pop( quantity ) AS Variance FROM sales_order_items GROUP BY Year, Quarter ORDER BY Year, Quarter
Year | Quarter | Average | Variance |
---|---|---|---|
2000 | 1 | 25.775148 | 203.9021... |
2000 | 2 | 27.050847 | 225.8109... |
... | ... | ... | ... |