with t1 as
(
     select '421022199911113425' c1 from dual
     union all
     select '242244555222114' from dual
     union all
     select '24224455522211124x' from dual
)

select decode(length(c1),15,1,18,2) c1
from t1 ;

      c1
-------------
1    2
2    1
3    2


select case when (select count(c1) from t1) <= 1 then 1 else 2 end c1
from dual; 

      c1
-------------
1    2

------解决方案--------------------
小写一个，可以参考一下
SQL code
CREATE TABLE message(id NUMBER(10),mid VARCHAR2(18),NAME VARCHAR2(20));
INSERT INTO message VALUES (1,'450902198711302756','xiao de');

CREATE OR REPLACE FUNCTION F_TEST_SFZHAO(p_mid VARCHAR2) RETURN NUMBER IS 
v_id NUMBER;
BEGIN 
  SELECT Length(mid) INTO v_id FROM message WHERE mid=p_mid AND ROWNUM=1;
  IF v_id=15 THEN 
    RETURN 1;
  ELSIF v_id=18 THEN 
    RETURN 2;
  END IF;
  EXCEPTION WHEN No_Data_Found THEN 
    RETURN 9;
END;

DECLARE 
v_return NUMBER;
BEGIN 
  v_return:=F_TEST_SFZHAO('45090219871130275');
  Dbms_Output.put_line(v_return);
END;

------解决方案--------------------
把第二个函数写了你看一下，不知道能否帮到你，我也是刚刚的学
create or replace function F_test_count(aac002 varchar2) return varchar2 is
v_count varchar2(2);
v_number number(8);  
begin
select count(aac002) into v_number from eaa8 ;
if v_number = 1 then  
v_count:=1;
else  
v_count:=2;
end if;
return v_count;
end;

------解决方案--------------------
探讨


引用:

小写一个，可以参考一下
SQL code
CREATE TABLE message(id NUMBER(10),mid VARCHAR2(18),NAME VARCHAR2(20));
INSERT INTO message VALUES (1,'450902198711302756','xiao de');

CREATE OR REPLACE FUN……