SQL 优化案例

create or replace procedure SP_GET_NEWEST_CAPTCHA(
v_ACCOUNT_ID in VARCHAR2,   --接收短信的手机号
v_Tail_num in VARCHAR2,     --尾号
v_result out VARCHAR2,      --结果
v_CAPTCHA out varchar2      --验证码
) is
l_recvmsgid         NUMBER;
begin
--取出验证码
if (not ((v_Tail_num is null) or (v_Tail_num = ' '))) and (not ((v_ACCOUNT_ID is null) or (v_ACCOUNT_ID = ' '))) then
   select in_msg_id,in_captcha
       into l_recvmsgid, v_CAPTCHA
       from( select t.msg_id in_msg_id, CAPTCHA in_captcha
         from jp_recvmsg_carcard t
         where t.tail_num = v_Tail_num
         and  t.account_id = v_ACCOUNT_ID
         and  t.msg_status = 0
         order by t.msg_time desc)
       where rownum = 1 ;
elsif (v_Tail_num is null) or (v_Tail_num = ' ') then
   select in_msg_id,in_captcha
       into l_recvmsgid, v_CAPTCHA
       from( select t.msg_id in_msg_id, CAPTCHA in_captcha
         from jp_recvmsg_carcard t
         where t.account_id = v_ACCOUNT_ID
         and  t.msg_status = 0
         order by t.msg_time desc)
       where rownum = 1 ;
elsif (v_ACCOUNT_ID is null) or (v_ACCOUNT_ID = ' ') then
   select in_msg_id,in_captcha
       into l_recvmsgid, v_CAPTCHA
       from( select t.msg_id in_msg_id, CAPTCHA in_captcha
         from jp_recvmsg_carcard t
         where t.tail_num = v_Tail_num
         and  t.msg_status = 0
         order by t.msg_time desc)
       where rownum = 1 ;
end if;

--更新状态
update jp_recvmsg_carcard t
         set t.msg_status = 1
         where t.msg_id = l_recvmsgid;
  commit;
  v_result:='0';
  EXCEPTION WHEN OTHERS THEN
     v_Result:='11111';
     ROLLBACK;
end SP_GET_NEWEST_CAPTCHA;

create or replace procedure SP_GET_NEWEST_CAPTCHA(
v_ACCOUNT_ID in VARCHAR2,   --接收短信的手机号
v_Tail_num in VARCHAR2,     --尾号
v_result out VARCHAR2,      --结果
v_CAPTCHA out varchar2      --验证码
) is
l_recvmsgid         NUMBER;
begin

  if(((v_Tail_num is null) or (v_Tail_num = ' ')) and  ((v_ACCOUNT_ID is null) or (v_ACCOUNT_ID = ' '))) then
     v_result:='11111';
     return;
  end if;
  --取出验证码
  select in_msg_id,in_captcha
         into l_recvmsgid, v_CAPTCHA
         from( select t.msg_id in_msg_id, CAPTCHA in_captcha
           from jp_recvmsg_carcard t
           where (t.tail_num = v_Tail_num or (((v_Tail_num is null) or (v_Tail_num = ' '))))
           and  (t.account_id = v_ACCOUNT_ID) or (((v_ACCOUNT_ID is null) or (v_ACCOUNT_ID = ' ')))
           and  t.msg_status = 0
           order by t.msg_time desc)
         where rownum = 1 ;

  --更新状态
  update jp_recvmsg_carcard t
           set t.msg_status = 1
           where t.msg_id = l_recvmsgid;
    commit;
    v_result:='0';
    EXCEPTION WHEN OTHERS THEN
       v_Result:='11111';
       ROLLBACK;
end SP_GET_NEWEST_CAPTCHA;

 优化案例2

SQL中的排序是很耗时的，根据测试按照时间排序比按照ID排序更耗时，所以如果可以，将按照时间排序改为按照ID排序；

如果必须按照时间排序，应该在时间列上加上索引！