Oracle 基于参数值需要执行的条件。

create or replace procedure fetch_ids(ename in varchar2,hiredate in date)
as
begin
select * from emp where empname=ename and join_date=hiredate ;

end;

if ename is null then
  select * from emp;
else
  select * from emp where empname=ename and join_date=hiredate ;
end if;

select * from emp 
where ( ename is not null and join_date=hiredate and empname=ename ) or
      ( ename is null) ;

execute immediate 'select * from emp ' || 
  case when ename is not null then
    'where empname=:ename and join_date=:hiredate'
  else 
    'where :ename is null and nvl(:hiredate, sysdate) is not null'
  end  
  using ename, hiredate