How to set all datasets from library?

[VaheMartirosyan]

How set all datasets from one library?

Datasets have different names.  I need to keep the Visit variable from all datasets.

Purpose: Understand that how many values the study has under the Visit variable. 

[ChrisNZ]

You could query the dictionary, or the view SASHELP.VCOLUMN, and keep all the entries with LIBNAME= your libname and NAME='VISIT'.

You might have to use the upcase function, I think not but I might be mistaken.

Be sure to clear as many libnames as possible beforehand to speed up reading the view.

[Edit: LIBNAME=, not MEMNAME= , sorry about that, late day reply..  ]

[VaheMartirosyan]

Let me try. Thanks

[Kurt_Bremser]

proc sql noprint;
select catx(".",libname,memname) !! " (keep=visit)" into :dsnames separated by " "
from dictionary.columns
where libname = "LIBNAME" and upcase(name) = "VISIT";
quit;

data all;
set &dsnames.;
run;

Note that there is a length limit for macro variables (65535), which might be reached if you have very many datasets with that variable in your library.

[ChrisNZ]

Another way, without macros and without using the potentially slow dictionary.

ods output members=MEMBERS; 
proc datasets lib=WORK mt=data;
run;
ods output close;

data _null_;
  set MEMBERS end=LASTOBS;
  if _N_=1 then call execute ('data _V/view=_V; set ');
  call execute(NAME);
  if LASTOBS then call execute(' indsname=_DS; DS=_DS; keep VISIT DS;run;');
run;
      
proc freq;
  tables VISIT;
run;

You can use variable DS if you want analysis by source (table name).