Question

我有下表

Id | cont
----------
 1 |  0
 2 |  1
 3 |  0
 4 |  1
 5 |  2
 6 |  3
 7 |  0
 8 |  1
 9 |  2
10 |  0
11 |  1
12 |  2
13 |  3
14 |  4

我需要获得序列号从2以上的岛屿，并删除间隙。

结果应为

Id | cont
----------
 5 |  2
 6 |  3
12 |  2
13 |  3
14 |  4

Answer 1

假设ID将单调增加，您可以通过几个步骤实现这一目标。

首先，对于每个数字，你得到第一个前一个零

select  t1.ID, t1.cont, max(t2.ID) max_id
from    yourTable t1
join    yourTable t2
on      t1.id >= t2.id
where   t2.cont = 0
group by t1.ID, t1.cont

然后使用它来获得多于1行的序列

select  t1.max_id, count(*)
from    (
            select  t1.ID, t1.cont, max(t2.ID) max_id /* STEP 1 */
            from    yourTable t1
            join    yourTable t2
            on      t1.id >= t2.id
            where   t2.cont = 0
            group by t1.ID, t1.cont
        ) t1
where   cont > 1
group by t1.max_id
having count(*) > 1

最后加入这两个来获取你想要的id和值

select  t1.id, t1.cont
from    (
            select  t1.ID, t1.cont, max(t2.ID) max_id /* STEP 1 */
            from    yourTable t1
            join    yourTable t2
            on      t1.id >= t2.id
            where   t2.cont = 0
            group by t1.ID, t1.cont

        ) t1
join    (
            select  t1.max_id, count(*) /* STEP 2 */
            from    (
                        select  t1.ID, t1.cont, max(t2.ID) max_id
                        from    yourTable t1
                        join    yourTable t2
                        on      t1.id >= t2.id
                        where   t2.cont = 0
                        group by t1.ID, t1.cont
                    ) t1
            where   cont > 1
            group by t1.max_id
            having count(*) > 1
        ) t2
on      t1.max_id = t2.max_id
where   t1.cont > 1

您可以在 here

中查看此查询

Answer 2

Or just..

SELECT DISTINCT x.* 
           FROM my_table x 
           JOIN my_table y 
             ON (y.id = x.id - 1 OR y.id = x.id + 1) 
            AND y.cont >= 2 
          WHERE x.cont >= 2;

MySql选择岛并按顺序删除间隙

2 个答案: