sql - 为一堆记录选择最小数据

Question

我有这张桌子：

我想为每串彩色记录找到最小的 date_time 值，即表格的结果将是这张表格。

需要哪个 SQL 命令？

标签： sqlsql-serverselectminimum

Answer 1

This is sort-of a gaps-and-islands problem. But the simplest way to think of it is as a simple lag():

select t.*
from (select t.*,
             lag(t.strand1) over (order by t.date_time) as prev_strand1
      from t
     ) t
where prev_strand1 is null or prev_strand1 <> strand1;