Question

我需要在此表中找到MTTF（平均故障时间）。

     machine_type_id    time    machine_id  event_type
      275                  0    97957590    0
      11148         64082917976 97957590    1
      11160         64508629318 97957590    0
      11565         94842321864 97957590    1
      11567         95269562076 97957590    0
      34517       2334183699633 97957590    1
      34519      2334580893038  97957590    0

其中，event_type = 0是机器添加或打开时，event_type= 1是机器发生故障时。 MTTF= total downtime /number of failure。

我的SQL脚本在从正确序列中添加的时间减去时间故障时遇到问题。例如，它可以在机器添加到池中的所有时间减去重新发生的故障。虽然它应该从上次机器添加池中减去。另一个问题是将总停机时间与故障数量分开的最后阶段。

我的SQL脚本是

select  o.machine_id, sum(o.timefailure- t.timeadded)/count(o.event_type) as MTTF
from 
    (
    select machine_id, machine_type_id ,time as timeadded 
    from machine_events 
    where event_type= 0 and machine_id=97957590 
    ) as t
INNER JOIN
    (
    select  machine_id,machine_type_id, event_type,time as timefailure
    from machine_events 
    where event_type = 1 and machine_id=97957590 
    ) as o
on o.machine_id=t.machine_id
where  o.timefailure- t.timeadded  <> 0 and  o.machine_type_id > t.machine_type_id 
group by o.machine_id

我将把简单数据用于测试

--INSERT INTO VALUES (   275,   0, 111, 0 );    
--INSERT INTO VALUES ( 11148,   4, 111, 1 );
--INSERT INTO VALUES ( 11160,   7, 111, 0 );
--INSERT INTO VALUES ( 11565,   17, 111, 1 );
--INSERT INTO VALUES ( 11567,   20, 111, 0 );
--INSERT INTO VALUES ( 34517,   40, 111, 1 );
--INSERT INTO VALUES ( 34519,   50, 111, 0 );

这里的总停机时间（4 + 10 + 20）。所以MTTF= Totaldowntime/number of failure

Answer 1

DROP TABLE deleteme_tbl;

CREATE TABLE deleteme_tbl
(
    machine_type_id    INT
  , time               INT
  , machine_id         INT
  , event_type         INT
);

INSERT INTO deleteme_tbl VALUES (   275,             0, 97957590, 0 );    
INSERT INTO deleteme_tbl VALUES ( 11148,   64082917976, 97957590, 1 );
INSERT INTO deleteme_tbl VALUES ( 11160,   64508629318, 97957590, 0 );
INSERT INTO deleteme_tbl VALUES ( 11565,   94842321864, 97957590, 1 );
INSERT INTO deleteme_tbl VALUES ( 11567,   95269562076, 97957590, 0 );
INSERT INTO deleteme_tbl VALUES ( 34517, 2334183699633, 97957590, 1 );
INSERT INTO deleteme_tbl VALUES ( 34519, 2334580893038, 97957590, 0 );

COMMIT;

WITH
    addset
    AS
        (SELECT machine_type_id
              , time
              , machine_id
              , event_type
           FROM deleteme_tbl
          WHERE event_type = 0),
    dropset
    AS
        (SELECT machine_type_id
              , time
              , machine_id
              , event_type
           FROM deleteme_tbl
          WHERE event_type = 1),
    finalset
    AS
        (SELECT addset.*
              , (SELECT MIN (time)
                   FROM dropset
                  WHERE dropset.machine_id = addset.machine_id
                    AND dropset.time > addset.time)
                    AS time_off
           FROM addset)
  SELECT machine_id, SUM (time_off - time) / COUNT (*) mttf
    FROM finalset
GROUP BY machine_id

减去不同记录中的值

1 个答案: