Datetime64 

Allows to store an instant in time, that can be expressed as a calendar date and a time of a day, with defined sub-second precision

Tick size (precision): 10-precision seconds

Syntax:

DateTime64(precision, [timezone])

Internally, stores data as a number of ‘ticks’ since epoch start (1970-01-01 00:00:00 UTC) as Int64. The tick resolution is determined by the precision parameter. Additionally, the DateTime64 type can store time zone that is the same for the entire column, that affects how the values of the DateTime64 type values are displayed in text format and how the values specified as strings are parsed (‘2020-01-01 05:00:01.000’). The time zone is not stored in the rows of the table (or in resultset), but is stored in the column metadata. See details in DateTime.

Examples 

1. Creating a table with DateTime64-type column and inserting data into it:

CREATE TABLE dt
(
    `timestamp` DateTime64(3, 'Europe/Moscow'),
    `event_id` UInt8
)
ENGINE = TinyLog
INSERT INTO dt Values (1546300800000, 1), ('2019-01-01 00:00:00', 2)
SELECT * FROM dt
┌───────────────timestamp─┬─event_id─┐
│ 2019-01-01 03:00:00.000 │        1 │
│ 2019-01-01 00:00:00.000 │        2 │
└─────────────────────────┴──────────┘
  • When inserting datetime as an integer, it is treated as an appropriately scaled Unix Timestamp (UTC). 1546300800000 (with precision 3) represents '2019-01-01 00:00:00' UTC. However, as timestamp column has Europe/Moscow (UTC+3) timezone specified, when outputting as a string the value will be shown as '2019-01-01 03:00:00'
  • When inserting string value as datetime, it is treated as being in column timezone. '2019-01-01 00:00:00' will be treated as being in Europe/Moscow timezone and stored as 1546290000000.

2. Filtering on DateTime64 values

SELECT * FROM dt WHERE timestamp = toDateTime64('2019-01-01 00:00:00', 3, 'Europe/Moscow')
┌───────────────timestamp─┬─event_id─┐
│ 2019-01-01 00:00:00.000 │        2 │
└─────────────────────────┴──────────┘

Unlike DateTime, DateTime64 values are not converted from String automatically

3. Getting a time zone for a DateTime64-type value:

SELECT toDateTime64(now(), 3, 'Europe/Moscow') AS column, toTypeName(column) AS x
┌──────────────────column─┬─x──────────────────────────────┐
│ 2019-10-16 04:12:04.000 │ DateTime64(3, 'Europe/Moscow') │
└─────────────────────────┴────────────────────────────────┘

4. Timezone conversion

SELECT
toDateTime64(timestamp, 3, 'Europe/London') as lon_time,
toDateTime64(timestamp, 3, 'Europe/Moscow') as mos_time
FROM dt
┌───────────────lon_time──┬────────────────mos_time─┐
│ 2019-01-01 00:00:00.000 │ 2019-01-01 03:00:00.000 │
│ 2018-12-31 21:00:00.000 │ 2019-01-01 00:00:00.000 │
└─────────────────────────┴─────────────────────────┘

See Also 

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