SQL删除具有相同值的所有连续记录,只留下第一个和最后一个

Question

我有一种情况,我需要删除共享相同字段值的连续记录("无法通知客户"),但我需要保留第一个和最后一个实例

样本数据

date             type    log
20/11/2014 09:05 System, Order Added
20/11/2014 09:18 Mark,   Invoice Printed
20/11/2014 10:00 System, Failed to notify Customer
20/11/2014 10:05 System, Failed to notify Customer
20/11/2014 10:10 System, Failed to notify Customer
20/11/2014 10:15 System, Failed to notify Customer
20/11/2014 10:20 System, Failed to notify Customer
20/11/2014 12:05 System, Order Completed

结果输出

date             type    log
20/11/2014 09:05 System, Order Added
20/11/2014 09:18 Mark,   Invoice Printed
20/11/2014 10:00 System, Failed to notify Customer
20/11/2014 10:20 System, Failed to notify Customer
20/11/2014 12:05 System, Order Completed

有没有办法制定一个SQL Server服务器查询来实现这一目标？对于我的生活,我无法理解我将如何接近这一点

Answer 1

试试这个：

样本数据 ：

use tempdb

create table temp(
    [date]  datetime,
    type    varchar(100),
    [log]   varchar(100)
)
insert into temp values
('11/20/2014 09:05', 'System', 'Order Added'),
('11/20/2014 09:18', 'Mark', 'Invoice Printed'),
('11/20/2014 10:00', 'System', 'Failed to notify Customer'),
('11/20/2014 10:05', 'System', 'Failed to notify Customer'),
('11/20/2014 10:10', 'System', 'Failed to notify Customer'),
('11/20/2014 10:15', 'System', 'Failed to notify Customer'),
('11/20/2014 10:20', 'System', 'Failed to notify Customer'),
('11/20/2014 12:05', 'System', 'Order Completed');

解决方案使用ROW_NUMBER()：

with cte as(
    select
        *,
        rn = row_number() over(partition by log order by [date]),
        cc = count(*) over(partition by log)
    from temp
    where
        log = 'Failed to notify Customer'
)
delete
from cte
where
    rn > 1 and rn < cc

select * from temp
drop table temp