SQL Server offers the following statistical functions.
| VAR | Returns the statistical variance of all values in the specified expression. |
| VARP | Returns the statistical variance for the population for all values in the specified expression |
| STDEV | Returns the statistical standard deviation of all values in the specified expression |
| STDEVP | Returns the statistical standard deviation for the population for all values in the specified expression |
All these functions return float.
The OVER clause may follow all aggregate functions except CHECKSUM.
Here is another sample to explain the relationships between SQL Server statistic functions:
USE AdventureWorks; GO SELECT STDEVP(Bonus) ‘Standard Deviation for the Population’, STDEV(Bonus) ‘Standard Deviation’, VAR(Bonus) ‘Variance’, STDEV(Bonus) * STDEV(Bonus) ‘VAR via STDEV’, VARP(Bonus) ‘Variance for the Population’, STDEVP(Bonus) * STDEVP(Bonus) ‘VARP via STDEVP’, VAR(Bonus) * (COUNT(Bonus)-1) / COUNT(Bonus) ‘VARP via VAR‘ FROM Sales.SalesPerson; GO |
