An enhanced version of the standard variance function is supported, generating either VAR_SAMP (expression) for the sample variance or VAR_POP (expression) for the population variance, while returning a value of type float. When dragging a Variance into a variable, the following tree element is created.
Columns and/or other non-aggregate expressions can be moved over the (empty) branch of the tree.
The enhancement consists of the ability to compute the variance of a date expression, generating for the sample version VAR_SAMP (date expression - DATE '1900-01-01').
The standard option to compute the variance over distinct values only is also provided, resulting in the generation for the sample version of VAR_SAMP(DISTINCT expression). Both this option as well as the options for population and sample versions of standard deviation are enabled through the Properties panel. Double-click on Standard Deviation, or highlight it and click Properties.