PROC SQL will give you the results of a many-to-many merge. You could also use a DATA step to do this, but it would take many DATA steps compared to one PROC SQL query. For example:

  proc sql;
   select *
   from dsn1,dsn2;
  quit;

To do a many-to-many merge based on a common variable, you will need to add the WHERE statement to the query. For example:

  proc sql;
   select *
   from dsn1,dsn2
   where dsn1.var=dsn2.var;
  quit;

See the SAS Guide to the SQL Procedure, Version 6, First Edition

or the

SAS Procedures Guide, Version 6, Third Edition for more information on PROC SQL.

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