Add inline function with IF/ELSE clause in Oracle 12c - oracle

Question

I have table A. If I make a query with inline function
with function f(n number) return varchar2 as
begin
return 'const string';
end;
select id, val, count, f(count) as value from A;
the result will be following:
ID VAL COUNT VALUE
---------- -------------------- ---------- ---------------
1 car 4 const string
2 building 15 const string
But if I try to make the function more complicated
with function f(n number)
return varchar2 as
begin
IF n < 5 THEN
return 'small';
ELSIF n < 50 THEN
return 'normal';
ELSE
return 'big';
END IF;
end;
select id, val, count, f(count) as value from A;
an error message appears:
with function f(n number)
*
ERROR at line 1:
ORA-00905: missing keyword
What's the problem here? Do I use right syntax for the command?

Answer 1

Your if statement is missing a then after the elsif condition clause, hence the missing keyword error pointing to function f. Also, after you fix this error you may get a ORA-00933: SQL command not properly ended pointing to the last semi-colon. Interestingly, the ";" does not seem to work as a terminator to the SQL statement when the PL/SQL declaration is included in the WITH clause. If we attempt to use it on its own, SQL*Plus waits for more text to be entered. So you have to end it with a / on a new line. Even in the example in SQL Reference manual uses a combination of ; and /. Here is my example I tested in PL/SQL Developer 11:
WITH
FUNCTION f(n number) return varchar2 IS
begin
if n<5 then
return 'small';
elsif (n>5 AND n<50) then
return 'medium';
else
return 'big';
end if;
end;
select f(25) from dual
/
Output:
F(25)
medium
EDIT: Also, change your AS to IS in your function definition.