Conditional Merge

[raivester]

I was wondering if anyone could share how to merge two data sets conditionally. The following is a simplified example of what I am trying to do. I have two data sets and each is unique at the individ_id_num and year level. The year variable ranges from 2000-2020.  I only want the merge to occur for year=2018. Is there some way to specify merge only if year=2018 in both data sets?

[PaigeMiller · Accepted solution]

data want;
    merge have1(where=(year=2018) in=in1) have2(where=(year=2018) in=in2);
    by indiv_id_num;
    if in1 and in2;
run;

Assumes have1 and have2 are properly sorted by indiv_id_num.

[raivester]

This worked, but the final data set only contains observations that met those conditional statements. Is there a way to retain all observations regardless of whether they merge given the specified conditions?