Conditional Insert using SAS Proc SQL - sql

Question

I am trying to add records from one smaller table into a very large table if the primary key value for the rows in the smaller table is not in the larger one:
data test;
Length B C $4;
infile datalines delimiter=',';
input a b $ c $;
datalines;
1000,Test,File
2000,Test,File
3000,Test,File
;
data test2;
Length B C $4;
infile datalines delimiter=',';
input a b $ c $;
datalines;
1000,Test,File
4000,Test,File
;
proc sql;
insert into test
select * from test2
where a not in (select a from test2);
quit;
This however insets no records into the table Test. Can anyone tell me what I am doing wrong? The end result should be that the row where a = 4000 should be added to the table Test.
EDIT:
Using where a not in (select a from test) was what I originally tried and it generated the following error:
WARNING: This DELETE/INSERT statement recursively references the target table. A consequence of this is a possible data integrity problem.
ERROR: You cannot reopen WORK.TEST.DATA for update access with member-level control because WORK.TEST.DATA is in use by you in resource
environment SQL.
ERROR: PROC SQL could not undo this statement if an ERROR were to happen as it could not obtain exclusive access to the data set. This
statement will not execute as the SQL option UNDO_POLICY=REQUIRED is in effect.
224 quit;
Thanks

Answer 1

You can either do the process in two steps. First create the table of records to insert and then insert them.
proc sql ;
create table to_add as
select * from test2
where a not in (select a from test)
;
insert into test select * from to_add ;
quit;
Or you could just change the setting for the UNDO_POLICY option and SAS will let you reference TEST while updating TEST.
proc sql undo_policy=none;
insert into test
select * from test2
where a not in (select a from test)
;
quit;