Question

我的表有4列：id（自动增量），机器（1到300之间的整数），事件（整数），状态（字符串）

我需要在这个表上运行一个查询，它返回具有最低机器号的四台机器，其中event =＆＃34; 5＆＃34;和状态=＆＃34;免费＆＃34;这是连续的数字。

例如，如果机器3忙，查询不应返回1,2,4,5，因为它们不是结果。相反，如果机器4,5,6,7是免费的，它应该返回那些。它不应该返回5,6,7,8，因为它不是最低的机器编号。最低的是4,5,6,7。

select * from mytable where event="5" and status="free" order by machine asc limit 4

正是我需要的，除了它确实返回所有行，而不考虑它们必须在机器列中结果。

可以这样做吗？

sample data as requested:

id - machine - event - status
22      1        5      free
23      2        5      free
24      3        5      busy
25      4        5      busy
26      5        5      free  *
27      6        5      free  *
28      7        5      free  *
29      8        5      free  *
30      9        5      free
31      10       5      busy
32      11       5      free

标有*的行是我需要的行。列机器上的前4个连续行，状态值为free，事件id = 5。

Answer 1

如果我理解正确，这应该可以解决问题

select  t1.id, t2.id, t3.id, t4.id
from    (select * from mytable where event="5" and status="free") t1
join    (select * from mytable where event="5" and status="free") t2
on      t1.id + 1 = t2.id
join    (select * from mytable where event="5" and status="free") t3
on      t1.id + 2 = t3.id
join    (select * from mytable where event="5" and status="free") t4
on      t1.id + 3 = t4.id
order by t1.id
limit 1

可能需要对连接条件进行一些调整（没有示例很难说）。

Answer 2

这样的事情应该有效

    SELECT SUBSTRING_INDEX(GROUP_CONCAT(machine ORDER BY machine),',',4) as machines FROM
(SELECT machine,
CASE WHEN machine=@machine + 1 THEN @n ELSE @n:=@n+1 END AS g,
    @machine := machine As m
  FROM
    t, (SELECT @n:=0) r, (SELECT @machine := '') z
WHERE event=5 and status="free"
  ORDER BY
    id) sub
    GROUP BY g 
    HAVING COUNT(*) >=4

如果你想要所有行

SELECT t.id,t.machine,t.event,t.status FROM
(SELECT id,machine,event,status,GROUP_CONCAT(id ORDER BY id) gr FROM
(SELECT *,
CASE WHEN machine=@machine + 1 THEN @n ELSE @n:=@n+1 END AS g,
    @machine := machine As m
  FROM
    t, (SELECT @n:=0) r, (SELECT @machine := '') z
WHERE event=5 and status="free"
  ORDER BY
    id) sub
    GROUP BY g 
    HAVING COUNT(*) >=4) o
JOIN t ON FIND_IN_SET(t.id,gr)
ORDER BY id LIMIT 4

Test

Test2

Answer 3

这取决于数据集的大小，但对于小数据集，这应该有效：

select * from mytable m1 where m1.event="5" and m1.status="free" 
and(m1.machine-1 in (select machine from mytable where event="5" and status="free") 
and m1.machine-2 in (select machine from mytable where event="5" and status="free") 
and m1.machine-3 in (select machine from mytable where event="5" and status="free") 
OR( m1.machine+1 in (select machine from mytable where event="5" and status="free") 
and m1.machine+2 in (select machine from mytable where event="5" and status="free") 
and m1.machine+3 in (select machine from mytable where event="5" and status="free") )
order by m1.machine asc limit 4

对于较大的数据集，您将需要使用JOIN来完成相同的操作。

您也可以使用后半部分找到第一个实例，然后从那里开始查询。

使用mysql查询找到具有特定值的4个连续行

3 个答案: