Equal Join of Two Files
by Dr. Alex Yu

Problem
There are two files: File A and File B. File A has some observations that File B doesn't have and vice versa. I want to merge two files if and only if the observations occur in both places.

Solution
In a relational database (RDE) this is so-called "equal join." You can do an equal join in a RDB by just dragging the field of one table to the identical field in another table. In SAS you do the following:

* Assume that in this case you have social security number in both files. * 

Data file_a; ...
		temp_id = ssn;
		proc sort; by ssn;

Data file_b; ...
		temp_id2 = ssn; 
		proc sort; by ssn;

Data all; merge file_a file_b; by ssn;
		if temp_id = temp_id2;