ORA-01722: invalid number while select numeric column and same numeric column reference in where - sql

Question

select id
from abc
where id = 1001;
return invalid number.
abc is a view
datatype of id is number
In create view cast is used
CREATE OR REPLACE VIEW abc AS
SELECT CAST (SUBSTR(T_ID,3,100) AS NUMBER) AS ID
from TEST
id column has all numeric values only
SELECT * FROM ABC WORKS FINE AND SO insert query works
tried below code which returns nothing in dbms output
declare
l_dummy number;
begin
for cur in (select ID from abc)
loop
begin
l_dummy := to_number(cur.ID);
exception
when others then dbms_output.put_line(cur.ID);
end;
end loop;
end;
column datatype nullable
ID NUMBER Yes 1 NO NO NO
SELECT *
FROM abc
WHERE
ID = 1001
returns:
ORA-01722: invalid number
01722. 00000 - "invalid number"
*Cause: The specified number was invalid.
*Action: Specify a valid number.

Answer 1

There are two problems:
SUBSTR(T_ID,3,100) will not return number always -- We need to consider the only numeric query
If we apply anything in WHERE condition of the view, Order of the execution of the WHERE condition is the call of Oracle optimizer.
Please see below code:
-- Data preparation
create table TEST (T_ID varchar2(20));
INSERT INTO TEST VALUES('AB1000'); -- Good data
INSERT INTO TEST VALUES('AB1001'); -- Good data
INSERT INTO TEST VALUES('CD1001'); -- Good data
INSERT INTO TEST VALUES('XY1004'); -- Good data
INSERT INTO TEST VALUES('XYZ1004'); -- Bad data
--
-- Data in the table
SELECT * FROM TEST;
Output
-- You need to create your view as following
-- rownum is used so that WHERE clause of view is executed first
-- and then any external WHERE clause on the view is executed
CREATE OR REPLACE VIEW ABC_NEWVIEW AS
SELECT
ID
FROM
(
SELECT
CAST(SUBSTR(T_ID, 3, 100) AS NUMBER) AS ID,
ROWNUM RN
FROM
TEST
WHERE
CASE
WHEN TRIM(TRANSLATE(SUBSTR(T_ID, 3, 100), '0123456789-,.', ' ')) IS NULL THEN 'numeric'
ELSE 'alpha'
END = 'numeric'
)
--
-- View
SELECT * FROM ABC_NEWVIEW
Output
-- Query using WHERE condition
SELECT *
FROM ABC_NEWVIEW
WHERE
ID = 1001
Output
You can find the demo in the following link:
DB Fiddle demo
You can see the demo of VIEW without ROWNUM:
Reproduced your issue -- So the issue is the order of the execution.
Cheers!!