SQL Server 2019

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select @@version;


(No column name)


Microsoft SQL Server 2019 (RTM-CU16) (KB5011644) - 15.0.4223.1 (X64) 
	Apr 11 2022 16:24:07 
	Copyright (C) 2019 Microsoft Corporation
	Express Edition (64-bit) on Windows Server 2019 Standard 10.0 <X64> (Build 17763: ) (Hypervisor)



CREATE TABLE test (
  dt datetime
);
INSERT INTO test
  VALUES
    ('2022-10-01 11:00:00'),
    ('2022-10-02 11:00:00'),
    ('2022-10-03 11:00:00'),
    ('2022-10-04 11:00:00'),
    ('2022-10-05 11:00:00'),
    ('2022-10-06 11:00:00'),
    ('2022-10-07 11:00:00'),
    ('2022-10-08 11:00:00'),
    ('2022-10-09 11:00:00'),
    ('2022-10-11 11:00:00'),
    ('2022-10-11 11:00:01'),
    ('2022-10-12 11:00:00'),
    ('2022-10-13 11:01:00')
;
13 rows affected

SELECT
  dt,
  DATEADD(MILLISECOND, pctcont_90_dt % 1000, DATEADD(SECOND, pctcont_90_dt / 1000, '19700101')) AS pctcont_90_dt,
  pctdisc_90_dt
  FROM (
    SELECT
      dt,
      CAST(
        percentile_cont(.90)
          WITHIN GROUP (ORDER BY (datediff_big(MS, '1970-01-01', dt)))
          OVER()
        AS BIGINT
      )
        AS pctcont_90_dt,
      percentile_disc(.90)
        WITHIN GROUP (ORDER BY dt) over()
        AS pctdisc_90_dt
    FROM test
  ) t
;


dt
pctcont_90_dt
pctdisc_90_dt


2022-10-01 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-02 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-03 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-04 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-05 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-06 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-07 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-08 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-09 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-11 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-11 11:00:01.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-12 11:00:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

2022-10-13 11:01:00.000
2022-10-12 06:12:00.200
2022-10-12 11:00:00.000

dt	pctcont_90_dt	pctdisc_90_dt
2022-10-01 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-02 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-03 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-04 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-05 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-06 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-07 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-08 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-09 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-11 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-11 11:00:01.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-12 11:00:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000
2022-10-13 11:01:00.000	2022-10-12 06:12:00.200	2022-10-12 11:00:00.000