Using large datasets in SAS ! Append Vs Set / Union.

Guys this is a intelligent tip !
I came across this while dealing with some of the huge dataloads .

Where to use it?! : Whenever adding to a huge dataset .

Code :

A)
PROC DATASETS;
APPEND OUT = membr_a
DATA = membr_b (WHERE=(year=2000));
RUN;

B)
DATA membr_a;
SET membr_a membr_b
(WHERE=(year=2000))

C)
Proc SQl;
create table xxx
select * from membr_a union select * from membr_b ;
quit;


Explanation of code:

A)
OUT --> is the output dataset to which you want to append.
Data --> is the new dataset , which you may want to add to the existing dataset (mentioned in out).

B) & C) --- i won't explain them , too trivial !


Advantage ??

The APPEND function is used to append observations from one dataset to another. Unlike the SET command which reads in all observations from the datasets being concatenated, the APPEND function only reads in the observations from the
dataset being appended. By using the APPEND function over the SET command you will save processing time and work
space

Options: "Force" option is always available when merged dataset are not exactly same !


Thanks,
KB