log function
Applies to: 
Databricks SQL Databricks Runtime
Returns the logarithm of expr with base.
Syntax
log( [base,] expr)
Arguments
base: An optional expression that evaluates to a numeric.expr: An expression that evaluates to a numeric.
Returns
A DOUBLE.
If base or expr are less than or equal to 0 the result is NULL.
log(expr) is a synonym for ln(expr).
Examples
SQL
> SELECT log(10, 100);
1.0
> SELECT log(e());
1.0