Suppose I have two variables a and b. a and b can be a positive integer or null. I'd like to set the conditions to select the elements:
- If both the variables are null values, it returns -1.
- If one of the variables is null, it returns the other variable.
- If no variable is null, it returns the smaller value of the two variables.
Is there any efficient DolphinDB function to obtain the result?
