A PL/SQL function returns a value, a procedure does not. Oracle is picky about this. The following, for example, will cause an error:
SQL> create or replace function unity
return integer
as
begin
return 1;
end;
/
begin
unity();
end;
/
show errors
2 3 4 5 6 7
Function created.
SQL> SQL> 2 3 4 unity();
*
ERROR at line 2:
ORA-06550: line 2, column 3:
PLS-00221: 'UNITY' is not a procedure or is undefined
ORA-06550: line 2, column 3:
PL/SQL: Statement ignored
Because
unity is a function, we must return its result into a variable...
SQL> declare
v_result integer;
begin
v_result := unity();
end;
/
show errors
2 3 4 5 6
PL/SQL procedure successfully completed.
I think Postgres is not as picky.
