SQLDeveloper Trigger Error report - ORA-00942: table or view does not exist - oracle

Question

I put this code into SQL Developer's Worksheet:
CREATE TRIGGER T_testDSNa
before INSERT
on testDSNa
referencing new as new
for each ROW
BEGIN
SELECT S_testDSN.nextval INTO :NEW.SYSID FROM dual;
END;
I get this:
Error report -
ORA-00942: table or view does not exist
00942. 00000 - "table or view does not exist"
*Cause:
*Action:
Would anyone know why? This has worked for 3 previous tables until I tried to run the DDL to create a 4th. Alternatively, is there a better way to set up an autoincrementing PK?

Answer 1

The problem was lack of schema. Oracle Definition of a schema :
Collection of database objects, including logical structures such as
tables, views, sequences, stored procedures, synonyms, indexes,
clusters, and database links. A schema has the name of the user who
controls it.
If you want to know the objects accessible without alias. You have to look on [USER_OBJECTS]. Which describes the relational objects owned by the current user :
SELECT
OBJECT_NAME
, OBJECT_TYPE
, LAST_DDL_TIME
FROM USER_OBJECTS;
If you want to know the objects accessible to the current user :
SELECT
OWNER
, OBJECT_NAME
, OBJECT_TYPE
, LAST_DDL_TIME
FROM ALL_OBJECTS;
In your case to see your objects in the list of available tables you need:
SELECT * FROM ALL_OBJECTS WHERE OWNER = 'USER';
You can also alter the session to avoid alias :
ALTER SESSION SET current_schema = User;
For priviliges/ roles views you can look at :
SELECT * FROM USER_SYS_PRIVS;
SELECT * FROM USER_ROLE_PRIVS;
The last method but not the most secure to avoid alias. Is to log on with a user that has the same name as the schema.
Hoping that it can help

Answer 2

I was getting the same issue.
Solution: What I observed that my table which I created was surrounded by double quotes, which made it case sensitive.
So for each time I refer to my table, I need to surround it by double quotes.
CREATE TRIGGER T_testDSNa
before INSERT
on "testDSNa"
referencing new as new
for each ROW
BEGIN
SELECT S_testDSN.nextval INTO :NEW.SYSID FROM dual;
END;
refer this link: What exactly do quotation marks around the table name do?