Proc copy of a few datasets, here the list of datasets is mentioned in another dataset

[Tommer]

Hello,

I have a dataset ds22 which lists the datasets that need to be copied over:

data ds22;
dataset="DM";
output;
dataset="SC";
output;
run;

The syntax used to copy them from f_ to o_ is:

data chk_;
   set ds22;
   call execute("proc copy in= f_ out=o_; select "||compress(dataset)||"; run;");
run;

Can someone help me understand how ||compress(dataset)|| works here to read the datasets called in ds22 individually?

[Reeza · Accepted solution]

It's calling PROC COPY for each data set. 

Change the code slightly to see the generated code more easily by adding a variable (STR) to hold the code.

Then view this CHK_ data set to see the code generated (note that I commented out the CALL EXECUTE so it won't run it in this one. 

CALL EXECUTE simply executes code snippets passed to it. The data step builds that statement dynamically using the "dataset" variable in the ds22 dataset. 

data chk_;
   set ds22;
   str = ""proc copy in= f_ out=o_; select "||compress(dataset)||"; run;";
   *call execute(str);
run;

proc print data=chk_ (obs=5);
var str;
run;

---

@Tommer wrote:

Hello,

I have a dataset ds22 which lists the datasets that need to be copied over:

data ds22;
dataset="DM";
output;
dataset="SC";
output;
run;

The syntax used to copy them from f_ to o_ is:

data chk_;
   set ds22;
   call execute("proc copy in= f_ out=o_; select "||compress(dataset)||"; run;");
run;

Can someone help me understand how ||compress(dataset)|| works here to read the datasets called in ds22 individually?

---

[Tommer]

Thank you Reeza!

I could not find any documentation on what --- select "||compress(dataset)||" does or how it works. I am only aware of pipe character for concatenation. Would you be able to provide any more info on how "||compress(dataset)||" reads as DM; SC etc?

[Tom]

---

@Tommer wrote:
Thank you Reeza!

I could not find any documentation on what --- select "||compress(dataset)||" does or how it works. I am only aware of pipe character for concatenation. Would you be able to provide any more info on how "||compress(dataset)||" reads as DM; SC etc?

---

I don't understand why that is the part that is confusing.  Those are concatenation operators.  The code is just placing the name of the dataset taken from the dataset variable DATASET in between two text strings. 

Perhaps adding more white space will make it clearer?

 call execute(
  "proc copy in= f_ out=o_; select "
|| compress(dataset)
|| "; run;"
   );

It is the CALL EXECUTION() function call that actually turns the resulting string into executed SAS code.

[Tommer]

Ah!! Writing it this way in the above post helped! I kept ready it incorrectly, my bad! Apologies. Just spent a lot of time reading it as---
select "||dataset||" . Thank you!!

[Tommer]

Please ignore this, I was reading the code incorrectly.

[Kurt_Bremser]

Since SELECT in PROC COPY accepts a list of dataset, you are better off doing it like this

proc sql noprint;
select dataset into :dsnames separated by " "
from ds22;
quit;

proc copy
  in= f_
  out=o_
;
select &dsnames.;
run;