If you try to overwrite the table you select from in PROC SQL, you might
encounter an error:

  ERROR: Close of OUTPUT file WORK.XYZ.DATA failed

The following code shows the problem:

   data test;
      value=1;
   run;
   proc sql;
      create table test
          as select * from test
       where value gt 0
         and value lt 0; /* where clause is always false */
   quit;

This construction (CREATE TABLE AS) is non-ansi compliant. It's
convenience to SAS customers, and is equivalent to a CREATE TABLE
followed by INSERT INTO. ANSI SQL/92 does not allow to insert data into
the same table that the data is coming from.

In SAS 9 we generate a warning:

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

In order to circumvent, don't use predicates that always resolves to
false or use a DATA Step:

  data test;
   set test;
   where value lt 0 and value gt 0;
  run;

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