spool c:\exp\cust.txt
Select name from cust;
spool off 

Declare Function foo (iStr IN VARCHAR2) 
RETURN VARCHAR2 IS

BEGIN
RETURN 'ffOkin ' || iStr ;
END;

Select foo(name) from cust;
spool c:\exp\cust.txt
spool off

ORA-00905: missing keyword
00905. 00000 -  "missing keyword"
*Cause:    
*Action:
Error at Line: 2 Column: 11

select * from v$version;
------------------------------------------------------------------------------------

Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
"CORE	11.2.0.2.0	Production"
TNS for 64-bit Windows: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

WITH
 FUNCTION get_domain(url VARCHAR2) RETURN VARCHAR2 IS
   pos BINARY_INTEGER;
   len BINARY_INTEGER;
 BEGIN
   pos := INSTR(url, 'www.');
   len := INSTR(SUBSTR(url, pos + 4), '.') - 1;
   RETURN SUBSTR(url, pos + 4, len);
 END;
SELECT DISTINCT get_domain(catalog_url)
  FROM product_information;
/
------------------------------------------------------------------------------------

ORA-00905: missing keyword
00905. 00000 -  "missing keyword"
*Cause:    
*Action:
Error at Line: 4 Column: 11

select * from v$version;

---------------------------------------------

Oracle Database 12c Standard Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
"CORE   12.1.0.2.0             Production"
TNS for 64-bit Windows: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production

WITH
FUNCTION get_domain(url VARCHAR2) RETURN VARCHAR2 IS
   pos BINARY_INTEGER;
   len BINARY_INTEGER;
BEGIN
   pos := INSTR(url, 'www.');
   len := INSTR(SUBSTR(url, pos + 4), '.') - 1;
   RETURN SUBSTR(url, pos + 4, len);
END;
SELECT DISTINCT get_domain(catalog_url)
  FROM product_information;

/

--Query result---------------------------------------------



ORA-06553: PLS-103: Encountered the symbol "end-of-file" when expecting one of the following:

   := . ( @ % ; not null range default character
06553. 00000 -  "PLS-%s: %s"
*Cause:    
*Action:
Error at Line: 4 Column: 1

--Script Output -------------------------------------------

Error starting at line 6 in command:
len BINARY_INTEGER
Error report:
Unknown Command

Error starting at line 7 in command:
BEGIN
   pos := INSTR(url, 'www.');
   len := INSTR(SUBSTR(url, pos + 4), '.') - 1;
   RETURN SUBSTR(url, pos + 4, len);
END;

SELECT DISTINCT get_domain(catalog_url)
  FROM product_information;
Error report:
ORA-06550: line 7, column 1:
PLS-00103: Encountered the symbol "SELECT" 
06550. 00000 -  "line %s, column %s:\n%s"
*Cause:    Usually a PL/SQL compilation error.
*Action:

-- НО:
SQL> WITH
  2  FUNCTION get_domain(url VARCHAR2) RETURN VARCHAR2
  3  IS pos BINARY_INTEGER
  4  ; len BINARY_INTEGER
  5  ; BEGIN   pos := INSTR(url, 'www.')
  6  ; len := INSTR(SUBSTR(url, pos + 4), '.') - 1
  7  ; RETURN SUBSTR(url, pos + 4, len)
  8  ; END
  9  ; SELECT DISTINCT get_domain(catalog_url)
 10    FROM (select 'https://www.favorite.site' catalog_url from dual) product_information
 11  /

GET_DOMAIN(CATALOG_URL)
--------------------------------------------------------------------------------
favorite

SQL>

set serveroutput on
spool ...
declaration
...
function xxx(...) as 
...
begin
for x in ( select * from table) loop
dbms_output.put_line(xxx(x));
end loop;
end;
/

-- НО:
SQL> WITH
  2  FUNCTION get_domain(url VARCHAR2) RETURN VARCHAR2
  3  IS pos BINARY_INTEGER
  4  ; len BINARY_INTEGER
  5  ; BEGIN   pos := INSTR(url, 'www.')
  6  ; len := INSTR(SUBSTR(url, pos + 4), '.') - 1
  7  ; RETURN SUBSTR(url, pos + 4, len)
  8  ; END
  9  ; SELECT DISTINCT get_domain(catalog_url)
 10    FROM (select 'https://www.favorite.site' catalog_url from dual) product_information
 11  /

GET_DOMAIN(CATALOG_URL)
--------------------------------------------------------------------------------
favorite

SQL>