Question

我有一张桌子：

$Email
      ->attachments(array(
            1 =>  WWW_ROOT . 'files' . DS. 'message_file' . DS . 'file'.DS.'9'.DS.'56b22b15b3cec.jpg'
        ))

我想知道哪些单位的序列大于3个零或大于重复的4个值。按年分组。所以，我的结果表是这样的：

 UNIT_ID | YEAR | MONTH |  VAR
---------+------+-------+------
    1    | 2015 |   1   |   0
    1    | 2015 |   2   |   0
    1    | 2015 |   3   |   0
    2    | 2015 |   1   |  10
    2    | 2015 |   2   |  10
    2    | 2015 |   3   |  10
    1    | 2015 |   4   |   5
    1    | 2015 |   5   |   5
    1    | 2015 |   6   |   5
    2    | 2015 |   4   |  10
    2    | 2015 |   5   |   3
    2    | 2015 |   6   |   3
    3    | 2016 |   1   |   3
    3    | 2016 |   2   |   3
    3    | 2016 |   3   |   3
    3    | 2016 |   4   |   3
    2    | 2016 |   6   |   0
    2    | 2016 |   7   |   0
    2    | 2016 |   8   |   0

我找到了this solution，但不幸的是我无法适应我的情况。我还需要查询是在MySQL中。

Answer 1

你可以加入他们4次。最后一次加入是left join，以允许3 0的情况。

select a.unit_id, a.year, 'true'
from tbl a
join tbl b on a.unit_id = b.unit_id and a.year = b.year and a.month+1 = b.month and a.var = b.var
join tbl c on b.unit_id = c.unit_id and b.year = c.year and b.month+1 = c.month and b.var = c.var
left join tbl d on c.unit_id = d.unit_id and c.year = d.year and c.month+1 = d.month and c.var = d.var
where a.var = 0 or d.var is not null;

更快，更通用的解决方案。它只扫描一次表，并使用用户定义的变量（前一个unit_id的@pu，前一年的@py等）来记住上一行：

select distinct unit_id, year
from (
  select unit_id, `year`, `month`, `var`, 
    if(unit_id=@pu and `year`=@py and `month`=@pm+1 and `var`=@pv, @i:=@i+1, @i:=1)*
    if(@pu:=unit_id,1,1)*if(@py:=`year`,1,1)*if(@pm:=`month`,1,1)*if(@pv:=`var`,1,1) as c
  from table1 a
  join (select @pu:=null, @py:=null, @pm:=null, @pv:=null, @i:=1) b
  order by unit_id, `year`, `month`, `var`) a
group by unit_id, `year`, `var`
having (`var` = 0 and max(c) >= 3) or (`var` != 0 and max(c) >= 4);

fiddle

如何使用MySQL识别依次重复值的实体？

1 个答案: