Oracle SQL : Retrieving non-existing values from IN clause - sql

Question

Having following query:
select table_name
from user_tables
where table_name in ('A','B','C','D','E','F');
Assuming only user_tables records B,C, and F exist, I want to retrieve the non-existing values A,D and E. This is a simple example, on real world the list can be huge.

Answer 1

A good way to generate fake rows is with a standard collection such as sys.odcivarchar2list:
select
tables_to_check.table_name,
case when user_tables.table_name is null then 'No' else 'Yes'end table_exists
from
(
select column_value table_name
from table(sys.odcivarchar2list('does not exist', 'TEST1'))
) tables_to_check
left join user_tables
on tables_to_check.table_name = user_tables.table_name
order by tables_to_check.table_name;
TABLE_NAME TABLE_EXISTS
---------- ------------
TEST1 Yes
does not exist No

Answer 2

if you have list of all those tables to be checked in Table1 then you can use NOT EXISTS clause
select name
from Table1 T1
where not exists ( select 1 from
user_tables U
where T1.name = U.table_name)

Answer 3

Only way is to use NOT EXISTS by converting the IN clause String into a Table of values.(CTE)
This is not a clean solution though. As The maximum length of IN clause expression is going to be 4000 only, including the commas..
WITH MY_STRING(str) AS
(
SELECT q'#'A','B','C','D','E','F'#' FROM DUAL
),
VALUES_TABLE AS
(
SELECT TRIM(BOTH '''' FROM REGEXP_SUBSTR(str,'[^,]+',1,level)) as table_name FROM MY_STRING
CONNECT BY LEVEL <= REGEXP_COUNT(str,',')
)
SELECT ME.* FROM VALUES_TABLE ME
WHERE NOT EXISTS
(SELECT 'X' FROM user_tables u
WHERE u.table_name = ME.table_name);

Answer 4

You can't. These values have to be entered into a temporary table at the least to do the desired operation. Also Oracle's IN clause list cannot be huge (i.e, not more than 1000 values).

Answer 5

Are you restricted to receiving those values as a comma delimited list?
instead of creating a comma delimited list with the source values, populate an array (or a table).
pass the array into a pl/sql procedure (or pull a cursor from the table).
loop through the array(cursor) and use a dynamic cusror to select count(table_name) from user_tables where table_name = value_pulled.
insert into table B when count(table_name) = 0.
then you can select all from table B
select * from tab1;
------------------
A
B
C
D
E
F
Create or replace procedure proc1 as
cursor c is select col1 from tab1;
r tab1.col1%type;
i number;
begin
open c;
loop
fetch c into r;
exit when c%notfound;
select count(tname) into i from tab where tname = r;
if i = 0 then
v_sql := 'insert into tab2 values ('''||r||''');
execute immediate v_sql;
commit;
end if;
end loop;
close c;
end proc1;
select * from tab2;
------------------
A
D
E
if this is not a one-off, then having this proc on hand will be handy.