ORACLE 存储过程 ORA-00900：无效SQL语句

CREATE OR REPLACE PROCEDURE proc_clrwl_ds1
(
  unit in nvarchar2,
)
is
  t number;
  adpt_name nvarchar2(50);
begin
  t:=40;
  if (t<=120) then 
  begin
  select dpt_name into adpt_name from usr_dpt;
  commit;
  end;
  else
  begin
  select dpt_name into adpt_name from usr_dpt where dpt_name=unit;  
  commit;  
  end;
  end if;
  commit;
end;

贴出SQL希望大家指正，只要我一执行就报ORA-00900，执行的SQL：exec proc proc_clrwl_ds1('')

具体的执行语句参数呢？