Proc SQL And UNION

There are five Union operators in Proc SQL. Four perform very different operations than the simple concatenation seen here – and several of those are very difficult to code in the SAS Data Step.

Union - matches by column position, not name, and drops duplicate rows

Union All - matches by column position, not name, and doesn’t drop duplicate rows

Union Corresponding - matches by column name and drops duplicate rows

Except - matches by column name and drops the rows found in both tables

Intersection - matches by column name and keeps the unique rows in both tables

The Unions can be combined also. Two tables could be concatenated with a Union Corresponding and then that result intersected with another table to find the records in the last table that were also in either the first table or the second.