表tb：表中无标识列和主键
Rdt ep Kid
2010-3-1 00:00:00 314.345 18
2010-3-1 00:00:00 347.174 17
2010-3-1 00:00:00 537.312 38
2010-3-1 00:30:00 314.343 18
2010-3-1 00:30:00 347.174 17
2010-3-1 00:30:00 537.313 38
2010-3-1 01:00:00 314.341 18
2010-3-1 01:00:00 347.171 17
2010-3-1 01:00:00 537.314 38
2010-3-1 01:30:00 314.335 18
2010-3-1 01:30:00 347.174 17
2010-3-1 01:30:00 537.313 38
2010-3-1 02:00:00 314.335 18
2010-3-1 02:00:00 347.174 17
2010-3-1 02:00:00 537.312 38
2010-3-1 02:30:00 314.322 18
2010-3-1 02:30:00 347.174 17
2010-3-1 02:30:00 537.312 38
........
按Kid分类，根据时间先后排序，如果后一条记录的ep减去前一条记录的ep得差值<0的话，就让后一条记录的ep=前一条记录的ep值。我用语句描述一下(语句是错误的，但是希望你们能看懂我的意思)
SQL code:
update tb
set ep=a.ep
from tb a
where ep<a.ep
and Kid=a.Kid
and Rdt=dateadd(mi,30,a.Rdt)
没人了啊，都回家了。我自己顶一下！
SQL code
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