It is possible to omit the DATA= option from a PROC statement, and the system will then use the last-created dataset for processing.
The stored value can be seen in the SYSLAST automatic macro variable; which has a default value of _NULL_ at the start of a new session.
The SYSLAST variable is one of those automatic variables whose value can be altered - simply submit code which generates a dataset, and the value will be updated.
Consider the code (submitted at the start of a new session):
%put &=syslast ; data over12 ; set sashelp.class ; where age > 12 ; run ; %put &=syslast ; proc print ; run ;
which generates values in the LOG as follows:
and produces a listing report.
Global System Option
This is not the only source of the last-created dataset, however. There is also a global system option _LAST_= which can specify any temporary, or permanent dataset. This over-rides the default value, and remains in force until another datset is created.
Amending the code, in a new session:
options _last_=sashelp.class ; proc print ; run ; data over12 ; set sashelp.class ; where age > 12 ; run ; proc print ; run ;
Listing reports of each of the SASHELP.CLASS and WORK.OVER12 datasets are produced.