mysql - 嵌套 while 循环比嵌套游标花费更多时间

Question

我从两个 sql 语句获取数据后插入 n 行。到目前为止我已经使用了两种方法，第一种是 Cursor，另一种是 While 循环。

嵌套光标:

    begin
    declare userId,taskId int default 0;
    declare userCnt int default 0;
    declare c1 cursor for select us_id from us_uxusermaster ;
    declare continue handler for not found set userCnt=1;
    open c1;
    CheckId: loop
    fetch c1 into userId;
    if userCnt=1
    then 
        leave CheckId;
    end if;
            Select pl.pl_minTarget into target from pl_planlist pl inner join ap_affiliateplan ap inner join us_uxusermaster us on Find_in_set(pl.pl_id,us.us_planListId) and ap.ap_id =us.us_taskPlanId where us_id=userId and pl.pl_serviceName=2;
                Begin
                DECLARE taskId int default 0;
                Declare taskCnt int default 0;
                Declare t1 cursor for select tk.tk_id  from tk_taskmaster tk where tk.tk_activeTime=AddDate(Current_date(),1)  and tk_actStatus=0 and tk_status=1 limit target;
                Declare continue handler for not found set taskCnt=1;
                open t1;
                CheckTask: loop
                fetch t1 into taskId;
                if taskCnt=1
                then
                leave CheckTask;
                end if;

                    insert into ut_userstask(ut_tk_id,ut_us_id,ut_edtm,ut_eby) values (taskId,userId,current_timestamp,'Via-Event');
                end loop checkTask;
                close t1;
                End;
    end loop CheckId;
    close c1;

    end;

While 循环:

    begin
declare taskName,taskCode,description,url,userLevel,TaskStatus,TaskActStatus,Steps,taskId,userId varchar(50);

declare activationTime,deActivationTime datetime;

Declare flag,flag2,counts,counts2 int default 0; 
Drop Temporary Table if exists temptrigg;
Set @rownumber=0;
Set @rownumber2=0;
create temporary table  temptrigg as(select * from (select (@rownumber := @rownumber + 1) AS newrow, us_id from us_uxusermaster) AS xst);
select count(*) into counts from temptrigg;
while(flag<counts)
Do
Set flag=flag+1;
Select us_id into userId from temptrigg where newrow=flag;

Drop Temporary Table if exists temptrigg2;
Create temporary table temptrigg2 as(select * from(select (@rownumber2 := @rownumber2 + 1) as newrow2,tk.tk_id  from tk_taskmaster tk where tk.tk_activeTime=Current_date()  and tk_actStatus=0 and tk_status=1)as xst);
Select count(*) into Counts2 from temptrigg2;
While(flag2<Counts2)
Do
Set flag2=flag2+1;
Select tk_id into taskId from temptrigg2 where newrow2=flag2;

    insert into ut_userstask(ut_tk_id,ut_us_id,ut_edtm,ut_eby) values (taskId,userId,current_timestamp,'Via-Event');

End While;
End While;

end

这里的问题是 while 循环花费的时间是光标的两倍。我对其 future 的结果感到困惑。通过替换嵌套的 while 循环来跟随光标会好吗？

插入 425 行时，游标耗时 23.05 秒，而 while 循环耗时 46 秒。这两个时间对我来说都太多了。有没有其他方法可以提高性能。

很高兴知道是否有。

Answer 1

我不确定我是否捕获了其中的每一项检查(尤其是限制)，但如果您可以将其压缩到单个插入中，那么会节省很多。像这样选择:

Insert into ut_userstask(ut_tk_id,ut_us_id,ut_edtm,ut_eby)
Select 
  tk.tk_id,
  us.us_id,
  current_timestamp,
  'Via-Event'
from pl_planlist pl 
inner join ap_affiliateplan ap 
inner join us_uxusermaster us on ap.ap_id = us.us_taskPlanId 
inner join tk_taskmaster tk on tk.tk_activeTime=AddDate(Current_date(),1) and tk_actStatus=0 and tk_status=1
where 
  pl.pl_serviceName=2
  and Find_in_set(pl.pl_id,us.us_planListId)

其他需要记住的事情:确保你有正确的索引并尽量避免像 FIND_IN_SET 这样的函数。这通常表明您的数据库没有足够规范化，并且使用速度非常慢，因为它绕过了列上可用的任何索引。

即使您不能将所有内容放入一个选择中，循环遍历主游标(例如获取用户)并为游标的每一行执行 insert..select 可能仍然更快。