Question

----------------
c_id  s_id   p_id    (customer_id, service_id, provider_id)
---- ---- ------  
1,     1,     1 - not elegible to select as next entry has same p_id
1,     2,     1
1,     3,     3

2,     1,     1
2,     2,     2
2,     3,     3

3,     1,     3 - not elegible to select as next entry has same p_id
3,     2,     3 - not elegible to select as next entry has same p_id
3,     3,     3

编写查询以从上述数据中产生以下结果的低成本方法是什么？

 ----------------
 c_id  s_id  p_id 
 ---- ---- ------ 
  1,    2,   1
  1,    3,   3

  2,    1,   1
  2,    2,   2
  2,    3,   3

  3,    3,   3

Answer 1

在MySQL 8.0中，您可以使用lead()来检索“下一个” p_id，并使用该信息来筛选出pid与下一个值相同的行。 / p>

select *
from (
    select t.*, lead(p_id) over(partition by c_id order by s_id) lead_p_id
    from mytable t
) t
where not p_id <=> lead_p_id

在早期版本中，通常会使用相关子查询：

select t.*
from mytable t
where not pid <=> (
    select p_id
    from mytable t1
    where t1.c_id = t.c_id and t1.s_id > t.s_id
    order by t1.s_id
    limit 1
)

Answer 2

我不太确定这是否最具成本效益，但它似乎是我能想到的最明显的解决方案。

select 
   c_id
   ,max(s_id) [s_id]
   ,p_id
from
  `table_name`
group by
   c_id
   ,p_id

Answer 3

如果s_id是无间隔的序列，则可以使用：

select t.*
from t left join
     t tnext
     on tnext.c_id = t.c_id and tnext.s_id = t.sid + 1
where not (tnext.p_id <=> t.p_id);

根据表中每个组的唯一列选择行

3 个答案: