variance aggregate function
Applies to: 
Databricks SQL Databricks Runtime
Returns the sample variance calculated from values of a group. This function is a synonym for var_samp aggregate function.
Syntax
variance ( [ALL | DISTINCT] expr ) [FILTER ( WHERE cond ) ]
This function can also be invoked as a window function using the OVER clause.
Arguments
expr: An expression that evaluates to a numeric.cond: An optional boolean expression filtering the rows used for aggregation.
Returns
A DOUBLE.
If DISTINCT is specified the function operates only on a unique set of expr values.
Examples
SQL
> SELECT variance(col) FROM VALUES (1), (2), (3), (3) AS tab(col);
0.9166666666666666
> SELECT variance(DISTINCT col) FROM VALUES (1), (2), (3), (3) AS tab(col);
1.0