If you have a many to many join, you can't use a merge statement.  A merge doesn't actually join tables together like SQL does so you end up with unexpected results if you have a many to many join.  You'll need to use proc sql.   proc sql;      create table New6 as      select N.*,           S.wanted_field1,           S.wanted_fiedl2      from New6 as N,           schduling_data3 as S      where N.provider = S.provider           and N.start_date between S.start_date and S.end_date; quit;   This presupposes that you have an end date and that the provider time periods do not overlap between provider records.  If not, you will end up with duplicate rows and you will need to make a determination of which provider row is the correct one.  You may be able to do that in the proc sql step or you may want to sort your data and select it out using a data step. ... View more

I would simply join by provider and then check your dates after the merge has occurred. proc sort data=New6; by provider; run; proc sort data=scheduling_data3; by provider; run; DATA NewData;      Merge New6(in=A) Scheduling_data3 (rename (start_date=prov_strt_dt)); by provider;      if A;      if start_date >= prov_strt_dt; run;   You probably also want to put a check in for the provider end date as well. ... View more