存储过程语法异常 帮忙看上 小妹是菜鸟

存储过程语法错误 大虾帮忙看下 小妹是初学者
if l_date=8 then ( if timeoffset=0 then let tmp_sjdm=F_GET_SJDM(proddate,0);
                      elif timeoffset=1 then (let tmp_date = to_char((date(substr('proddate',5,2)||'/01/'||substr('proddate',1,4))- 1 ),'%Y%m%d');
                                              let tmp_sjdm= F_GET_SJDM(tmp_date,0);
                                             )                       
                      elif timeoffset=2 then (let tmp_date = to_char((date(substr('proddate',5,2)||substr('proddate',7,2)||substr('proddate',1,4))- 1 UNITS YEAR),'%Y%m%d');
                                              let tmp_sjdm= F_GET_SJDM(tmp_date,0);
                                             ) 
                      elif  timeoffset=3 then (let tmp_date = to_char((date('01/01/'||substr('proddate',1,4))- 1 ),'%Y%m%d');
                                              let tmp_sjdm= F_GET_SJDM(tmp_date,0);
                                             )
                   end if;
                 )
  elif l_date=7 then (if timeoffset=0 then let tmp_sjdm=F_GET_SJDM(proddate,1);
                      elif timeoffset=1 then (let tmp_date = to_char((date(substr('proddate',5,2)||'/01/'||substr('proddate',1,4))- 1 ),'%Y%m')||'3';
                                              let tmp_sjdm= F_GET_SJDM(tmp_date,1);
                                             )