SQLite 3.27

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-- Тестовый набор данных:

with

test1 (field1, field2) as

(

select '2020-12-01 01:54:40.112000' as field1, 1521.731812 as field2 union all

select '2020-12-01 01:54:41.112000' as field1, 1521.731812 as field2 union all

select '2020-12-01 01:54:42.112000' as field1, 1521.731812 as field2 union all

select '2020-12-01 01:54:43.112000' as field1, 1521.695557 as field2 union all

select '2020-12-01 01:54:44.112000' as field1, 1521.695557 as field2 union all

select '2020-12-01 01:54:45.112000' as field1, 1521.731812 as field2 union all

select '2020-12-01 01:54:46.112000' as field1, 1521.695557 as field2 union all

select '2020-12-01 01:54:47.112000' as field1, 1521.695557 as field2 union all

select '2020-12-01 01:55:18.112000' as field1, 1521.623291 as field2 union all

select '2020-12-01 01:55:19.112000' as field1, 1521.695557 as field2 union all

select '2020-12-01 01:55:49.112000' as field1, 1521.695557 as field2

)

-- Основной запрос:

select v.field1, v.field2

from (

select t0.field1, t0.field2

, (

select t1.field2

from test1 as t1

where t1.field1 < t0.field1

order by t1.field1 desc

limit 1

) as pev_field2

from test1 as t0

) as v

where case v.pev_field2

when v.field2 then 0

else 1

end = 1