How to count the number of missing values?

I have a simple question I would like to know asap. How I can count the number of missing (or NULL) values in distinct from 0 values?

Note Added

I have tried to use some functions listed below, but I don't know if these functions could distinguish the missing values from 0 values.
  • mdesc
  • missings
Please kindly give me any answers or comments to me!