topic Re: check if data set has Index in SAS Programming

check if data set has Index

Ronein — Wed, 19 Feb 2025 10:10:00 GMT

Hello

In order to check if a data set has index I saw the following code:

%let dsid=%sysfunc(open(sashelp.cars));
%put dsid=&dsid; /**2**/

%let indx=%sysfunc(attrn(&dsid,isindex));
%put indx=&indx; /**0**/

My question-

&dsid get value 2

what does it mean?

What exactly &dsid is calculating?

In code : %let indx=%sysfunc(attrn(&dsid,isindex));

why the argument is &dsid and not data set name (sashelp.cars)?

http://support.sas.com/kb/43/637.html

Re: check if data set has Index

Patrick — Wed, 19 Feb 2025 10:37:20 GMT

From the docu for the OPEN Function

The OPEN function opens a SAS data set, DATA step, or a SAS SQL view and returns a unique numeric data set identifier, which is used in most other data set access functions. OPEN returns 0 if the data set could not be opened.

From experience:

The first time you use the open() function in a SAS session, the function will return a value of 1 if successful. Any time you execute the function again in the same session the return value gets incremented by 1.

Think of this value as a pointer to your opened data set that you then use in other functions.

Re: check if data set has Index

Tom — Wed, 19 Feb 2025 14:11:56 GMT

The value returned by OPEN() is the something called a "file handle" in a lot of programming languages. It is essentially a pointer to the open file that you can pass to other functions that operate on files, like the ATTRN() function (and the CLOSE() function) used in that example.

You cannot just use the filename (or in this case the dataset name) because you might have the same dataset open multiple times for different purposes.

Consider this simple SAS program to do a quick sort of SASHELP.CLASS by SEX.

data class ;
  set sashelp.class(where=(sex='F'))
      sashelp.class(where=(sex='M'))
  ;
run;

Re: check if data set has Index

yabwon — Wed, 19 Feb 2025 14:40:49 GMT

I highly recommend Maxim number 1, it's not that hard to do.

Open() Function - Details:

https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.5/lefunctionsref/n0q72zlfmfjplon1p3nprf85sdin.htm#p0yd54ov2r2wn5n1or7xz6czlh13

Bart