--经测，没问题
SQL> create table T_PJ_GDL(XZQ_DM varchar2(20),NF int,YF int,GDL float);

表已创建。

SQL> insert into T_PJ_GDL values('4401',2012,9,0.7);

已创建 1 行。

SQL> CREATE OR REPLACE FUNCTION F_PJ_GDL_SCORE(mXZQDM VARCHAR2,
  2  mNF INT, mYF INT, mFZ FLOAT)
  3  RETURN FLOAT IS
  4    VSCORE FLOAT;
  5  BEGIN
  6    SELECT
  7    (CASE WHEN GDL>=0.75 THEN mFZ
  8    WHEN GDL<0.75 AND GDL>=0.70 THEN (mFZ - 1*1.5)
  9    WHEN GDL<0.70 AND GDL>=0.65 THEN (mFZ - 2*1.5)
 10    WHEN GDL<0.65 AND GDL>=0.60 THEN (mFZ - 3*1.5)
 11    WHEN GDL<0.60 AND GDL>=0.55 THEN (mFZ - 4*1.5)
 12    WHEN GDL<0.55 AND GDL>=0.55 THEN (mFZ - 5*1.5)
 13    WHEN GDL<0.50 AND GDL>=0.55 THEN (mFZ - 6*1.5)
 14    WHEN GDL<0.45 AND GDL>=0.55 THEN (mFZ - 7*1.5)
 15    WHEN GDL<0.40 AND GDL>=0.55 THEN (mFZ - 8*1.5)
 16    WHEN GDL<0.35 AND GDL>=0.30 THEN (mFZ - 9*1.5)
 17    ELSE 0
 18    END ) as FS INTO vSCORE FROM T_PJ_GDL
 19    WHERE XZQ_DM=mXZQDM AND NF=mNF AND YF=mYF;
 20    RETURN vSCORE;
 21  END;
 22  /

函数已创建。

SQL> select F_PJ_GDL_SCORE('4401',2012,9,15) from dual;

F_PJ_GDL_SCORE('4401',2012,9,15)                                                
--------------------------------                                                
                            13.5