how to find the execution plan of proc sql?

[kwu]

I would like to know how SAS proc sql process a query and see what type of join it performs and if I should use a proc sql or a data step.

Any information about the sql query optimizer, or how optimizer comes up the execution plan would be a great help.
Thanks in advance.

[chang_y_chung_hotmail_com]

There is undocumented _method option to the proc sql statement. See also Kent's note at
http://support.sas.com/techsup/technote/ts553.html