/*
Merging data
*/
*First we read in a test data set for you;
data mydata;
 input OBS Y VAR1 VAR2 VAR3;
cards;
1 1	10	33	4
2 0	20	21	3
3 1	30	59	2
17 1	20	76	1
5 2	.	24	3
6 0	20	22	2
7 1	10	28	2
8 1	10	49	2
9 0	30	76	2
10 2 20	59	2
;

*Creating an additional dataset (5 observations) for merging illustration ;
data test(keep=var4-var6 OBS);
 set mydata;
 OBS=_n_;
 VAR4=Var1*10;
 VAR5=VAR2*10;
 VAR6=VAR3*10;
 if OBS>5 then delete;
run;

*must always remember to sort tables based on what you plan to join them with;
proc sort data=mydata;by OBS;run;
proc sort data=test;by OBS;run;

*Example 1 - Include all observations from first table (Mymodel);
Data merged;
merge mydata (in=a) test ;
by OBS;
if a;
run;
Title Merged Table (Include all from First table);
proc print data=merged;run;
*Example 2 - Include only observations from second table (test);
Data merged;
merge mydata (in=a) test(in=b);
by OBS;
if  b;
run;
Title Merged Table (Include all from 2nd table);
proc print data=merged;run;
*Example 2 - Include only observations common to both);
Data merged;
merge mydata (in=a) test(in=b);
by OBS;
if  a and b;
run;
Title Merged Table (Include observations common to both);
proc print data=merged;run;