WARNING and ERROR messages in SAS serve a useful purpose, but there are certain situations where the message is known, anticipated, and it may be deemed acceptable to suppress it.

One such example is the message:

WARNING: This CREATE TABLE statement recursively references the target table. A consequence of this is a possible data integrity problem

when writing a SAS dataset back over itself in PROC SQL.

In DATA step syntax, it is not uncommon to generate a dataset, then write back over the dataset in a subsequent process (although some developers prefer not to), e.g.

data boys (drop = sex) ;
  set sashelp.class ;
    where sex = 'M' ;
run ;

data boys ;
  set boys ;
    name = upcase(name) ;
run ;

No messages are written to the LOG advising that the dataset will be altered during the subsequent process.

Performing a comparable process in PROC SQL:

proc sql noprint ;
  create table girls as
    select *
    from sashelp.class
    where sex = 'F'
    ;
quit ;

proc sql noprint ;
  create table girls as 
    select  upcase(name) as name
	   ,age
	   ,height
	   ,weight
    from girls
    ;
quit ;

generates the WARNING message in the LOG. 

The message is generated as a consequence of the default setting of a GLOBAL System Option:

options sqlundopolicy = required | optional | none ;

The possible values denote:

* Default action

The disparity between the DATA step and PROC SQL solutions may result in a developer electing to suppress the WARNING message, and this can be done, either by changing the Global System Option, or by over-riding the Global System Option with an option on a PROC SQL statement.

Either of:

options sqlundopolicy = none ;

or

proc sql undo_policy = none ;

will suppress the WARNING. 

As with many such SAS options the statement option takes precedence over the Global option.