Question

我在mysql query, return rows when condition is satisfied

上发布了更新的问题

感谢那些帮助过......

好的，我正在对此进行第二次尝试，因为我搞砸了原来的问题。我已经更正了日期格式以匹配mysql。此外，我实际上是根据值的百分比在查询中存档状态值，即，如果它在最高观察值的85％以内，则标记为高，如果它在低水位的15％内，则标记为低。

其格式为name，test_date，score。

类似

John, 2014-10-12, 87
John, 2014-10-13, 87
John, 2014-10-14, 33
John, 2014-10-15, 32
John, 2014-10-16, 44
John, 2014-10-17, 87
John, 2014-10-18, 89
John, 2014-10-19, 90
Jane, 2014-10-12, 32
Jane, 2014-10-13, 87
Jane, 2014-10-14, 33
Jane, 2014-10-15, 88
Jane, 2014-10-16, 44
Jane, 2014-10-17, 87
Jane, 2014-10-18, 89
Jane, 2014-10-19, 90

以下是我当前必须返回仅在高水位线或低水位线内的数据的查询。

select userdata.name, test_date, score, if(score >=.85*temp.High,"High","Low") from userdata inner join (select name, Min(score) as Low, Max(score) as High from userdata where (test_date between '2013-12-02' and '2014-12-01') group by name) as temp on userdata.name=temp.name where (score >= .85*temp.High or score <= 1.15*temp.Low) and test_date between '2013-12-02' and '2014-12-01' order by name, test_date

假设最高为96，最低为35，则返回

等数据

 John, 2012-12-02, 90, High
 John, 2012-12-03, 40, Low
 John, 2012-12-04, 41, Low
 John, 2012-12-05, 95, High
 John, 2012-12-05, 94, High
 John, 2012-12-02, 90, High
 Jane, 2012-12-03, 40, Low
 Jane, 2012-12-04, 41, Low
 Jane, 2012-12-05, 41, Low 
 Jane, 2012-12-06, 41, Low
 Jane, 2012-12-06, 41, Low
 Jane, 2012-12-11, 89, High

现在我想看看我是否可以修改我的查询以仅返回更改状态。我查看了所提供的答案，但是我将我们的元素与原始查询结合起来以产生所需的结果。感谢您已经给出的帮助，我为第一次没有正确填写我的问题而道歉。

Answer 1

您可以使用变量或获取以前的状态来执行此操作。这是第二种方法：

select t.*
from (select t.*,
             (select t2.state
              from onetable t2
              where t2.name = t.name and t2.date < t.date
              order by t2.date desc
              limit 1
             ) as prev_state
      from onetable t
     ) t
where prev_state is null or prev_state <> state;

为了提高性能，您需要onetable(name, date, state)上的索引。

Answer 2

你可以使用MySQL变量来做到这一点。

每当日期不匹配且条件不匹配时，您可以标记该行

您需要按名称和日期对行进行排序，以便比较相邻日期。

SQL Fiddle

select name,  prevDate, prevCondition
from
(
select name, `date`, `value`, `condition`,
       case when `date`<> @prevDate  and `condition` <> @prevCondition 
       then 1 
       else 0 
       end as flag,
@prevDate := date AS prevDate,
@prevCondition := `condition` AS prevCondition
from table1, ( select @prevCondition:= NULL , @prevDate = NULL) as t
order by name, `date` )T
where T.flag =1

mysql查询以识别状态的变化

2 个答案: