mysql - mysql中如何统计连续的重复行

Question

我们在客户表中有两列，其中包含客户 ID 和服务 ID。因此，对于每个使用多项服务的客户，我们必须找到客户使用的连续服务的最大数量。

create table customer(id int not null auto_increment,customerid varchar(20), serviceid varchar(20),primary key(id));

insert into customer(customerid,serviceid) values('Nitesh','Mobile');
insert into customer(customerid,serviceid) values('Nitesh','Mobile');
insert into customer(customerid,serviceid) values('Nitesh','Landline');
insert into customer(customerid,serviceid) values('Nitesh','Broadband');
insert into customer(customerid,serviceid) values('Nitesh','Mobile');

insert into customer(customerid,serviceid) values('Nishant','Mobile');
insert into customer(customerid,serviceid) values('Nishant','Landline');
insert into customer(customerid,serviceid) values('Nishant','Landline');
insert into customer(customerid,serviceid) values('Nishant','Landline');
insert into customer(customerid,serviceid) values('Nishant','Broadband');

insert into customer(customerid,serviceid) values('Soe','Mobile');
insert into customer(customerid,serviceid) values('Soe','Mobile');
insert into customer(customerid,serviceid) values('Soe','Landline');
insert into customer(customerid,serviceid) values('Soe','Broadband');
insert into customer(customerid,serviceid) values('Soe','Mobile');

我必须统计客户连续使用的最大服务。

输出:

Customerid|Serviceid|ServiceidCount
----------------------------------

Nitesh|Mobile|2
Nishant|Landline|3
Soe|Mobile|2

Answer 1

假设您有一个指定顺序的列，例如 id。

然后你可以使用变量来做到这一点:

select customer, max(rn) as serviceidcnt,
       substring_index(group_concat(serviceid order by rn desc)) as serviceid
from (select c.*,
             (@rn := if(@cs = concat_ws(':', customerid, serviceid), @rn + 1,
                        if(@cs := concat_ws(':', customerid, serviceid), 1, 1)
                       )
             ) as rn
      from customer c cross join
           (select @rn := 0, @cs := '') params
      order by c.customer, ??
     ) cs
group by customer;

?? 是用于排序的列。

注意:获取服务 ID 需要使用依赖于 group_concat() 的 MySQL“hack”。默认情况下，这限制为大约 1000 字节的内部缓冲区大小。这可以更改。