topic sas dataset with index in SAS Programming

sas dataset with index

HeatherNewton — Tue, 25 Oct 2022 06:39:40 GMT

Hi if I have created an index for my dataset, does that mean sorting is not required anymore for this dataset prior to merging? As I see this in some programs with index where sort is not added before merge..

Re: sas dataset with index

PeterClemmensen — Tue, 25 Oct 2022 06:49:49 GMT

Yes. Though, all the data sets in the Merge Statement must be either sorted or have an appropriate index.

See the small example below

data one;
input x y1;
datalines;
1 10
3 20
2 30
;

data two;
input x y2;
datalines;
1 40
2 50
3 60
;

proc datasets lib = work nolist;
   modify one;
   index create x;
run;quit;

data want;
   merge one two;
   by x;
run;

Re: sas dataset with index

LinusH — Tue, 25 Oct 2022 08:56:34 GMT

Even if it's technically possible to merge on indexed variables, it's seldom a good idea.

In most situations sorting is much faster.

Re: sas dataset with index

Kurt_Bremser — Tue, 25 Oct 2022 08:28:14 GMT

I've never used indexes for sorting. Indexes are only good when you need to extract a small (read: 10% or less) subset of the dataset. In all other cases, they only add additional I/O and therefore processing time.