SQL & PL/SQL

I wanted to test some SQL to make sure it was SQL 92 compliant. My understanding is that the command I was using was compilant.

I set on the validator:

ALTER SESSION SET flagger=FULL;

and issued the statement:

SELECT
COALESCE(
NULL, 34, 13, 0
)
from
dual;

But I get the error:

ERROR at line 4:
ORA-00097: use of Oracle SQL feature not in SQL92 Full Level
ORA-06550: line 4, column 1:
PLS-01413: Use of NULL an expression
ORA-06550: line 3, column 1:
PLS-01416: Use of <id> (<value>...) here

So I tried this:

SELECT
COALESCE(
'', 34, 13, 0
)
from
dual;

But get:

ERROR at line 4:
ORA-00097: use of Oracle SQL feature not in SQL92 Full Level
ORA-06550: line 4, column 3:
PLS-01466: Null strings are not allowed
ORA-06550: line 3, column 1:
PLS-01416: Use of <id> (<value>...) here

Any ideas what I am doing wrong, please?

Thanks