how to write a macro variable into existing dataset?

[Tom]

You can query metadata from some systems to get record counts, but that does not work for all.  For example for VIEWs.

That is why the code I posted included this statement.

  where missing(table_cnt);

[Ivan555]

@Patrick 

About:

If you have to care about performance then don't issue a select count(*) against SAS tables as there the row count is a table attribute (nlobs) which you can retrieve directly from the descriptor (metadata) part of the table.

I have missing values in all descritor parts..

Previosly you wrote:

Tables from libraries that point to databases will have a missing value for the row count because that's not a table attribute of database tables (like it is for SAS tables).

I think that is my case, so I have to calculate metadata for several libraries consisting of ~500 tables manually.. but this will be another topic I think.

I think during September I will write a code being based on your and Tom's solution.

I also think I will post it for information and will make a link on this discussion.

One more time:  Big THX for Everyone, I am closing the topic.