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Merge pull request #63271 from jrdi/doc-week-start

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Document start of week differences
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Nikolay Degterinsky 2024-05-02 12:32:48 +00:00 committed by GitHub
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docs/en/sql-reference/functions/date-time-functions.md
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@ -1413,9 +1413,10 @@ toStartOfFifteenMinutes(toDateTime('2023-04-21 10:20:00')): 2023-04-21 10:15:00
toStartOfFifteenMinutes(toDateTime('2023-04-21 10:23:00')): 2023-04-21 10:15:00 toStartOfFifteenMinutes(toDateTime('2023-04-21 10:23:00')): 2023-04-21 10:15:00
``` ```
## toStartOfInterval(date_or_date_with_time, INTERVAL x unit \[, time_zone\]) ## toStartOfInterval
This function generalizes other `toStartOf*()` functions. For example, This function generalizes other `toStartOf*()` functions with `toStartOfInterval(date_or_date_with_time, INTERVAL x unit [, time_zone])` syntax.
For example,
- `toStartOfInterval(t, INTERVAL 1 year)` returns the same as `toStartOfYear(t)`, - `toStartOfInterval(t, INTERVAL 1 year)` returns the same as `toStartOfYear(t)`,
- `toStartOfInterval(t, INTERVAL 1 month)` returns the same as `toStartOfMonth(t)`, - `toStartOfInterval(t, INTERVAL 1 month)` returns the same as `toStartOfMonth(t)`,
- `toStartOfInterval(t, INTERVAL 1 day)` returns the same as `toStartOfDay(t)`, - `toStartOfInterval(t, INTERVAL 1 day)` returns the same as `toStartOfDay(t)`,
@ -1440,6 +1441,8 @@ The calculation is performed relative to specific points in time:
(*) hour intervals are special: the calculation is always performed relative to 00:00:00 (midnight) of the current day. As a result, only (*) hour intervals are special: the calculation is always performed relative to 00:00:00 (midnight) of the current day. As a result, only
hour values between 1 and 23 are useful. hour values between 1 and 23 are useful.
If unit `week` was specified, `toStartOfInterval` assumes that weeks start on Monday. Note that this behavior is different from that of function `toStartOfWeek` in which weeks start by default on Sunday.
**See Also** **See Also**
- [date_trunc](#date_trunc) - [date_trunc](#date_trunc)
@ -1673,7 +1676,7 @@ Like [fromDaysSinceYearZero](#fromDaysSinceYearZero) but returns a [Date32](../.
Returns the `unit` component of the difference between `startdate` and `enddate`. The difference is calculated using a precision of 1 nanosecond. Returns the `unit` component of the difference between `startdate` and `enddate`. The difference is calculated using a precision of 1 nanosecond.
E.g. the difference between `2021-12-29` and `2022-01-01` is 3 days for `day` unit, 0 months for `month` unit, 0 years for `year` unit. E.g. the difference between `2021-12-29` and `2022-01-01` is 3 days for `day` unit, 0 months for `month` unit, 0 years for `year` unit.
For an alternative to `age`, see function `date\_diff`. For an alternative to `age`, see function `date_diff`.
**Syntax** **Syntax**
@ -1742,14 +1745,14 @@ Result:
``` ```
## date\_diff ## date_diff
Returns the count of the specified `unit` boundaries crossed between the `startdate` and the `enddate`. Returns the count of the specified `unit` boundaries crossed between the `startdate` and the `enddate`.
The difference is calculated using relative units, e.g. the difference between `2021-12-29` and `2022-01-01` is 3 days for unit `day` (see [toRelativeDayNum](#torelativedaynum)), 1 month for unit `month` (see [toRelativeMonthNum](#torelativemonthnum)) and 1 year for unit `year` (see [toRelativeYearNum](#torelativeyearnum)). The difference is calculated using relative units, e.g. the difference between `2021-12-29` and `2022-01-01` is 3 days for unit `day` (see [toRelativeDayNum](#torelativedaynum)), 1 month for unit `month` (see [toRelativeMonthNum](#torelativemonthnum)) and 1 year for unit `year` (see [toRelativeYearNum](#torelativeyearnum)).
If unit `week` was specified, `date\_diff` assumes that weeks start on Monday. Note that this behavior is different from that of function `toWeek()` in which weeks start by default on Sunday. If unit `week` was specified, `date_diff` assumes that weeks start on Monday. Note that this behavior is different from that of function `toWeek()` in which weeks start by default on Sunday.
For an alternative to `date\_diff`, see function `age`. For an alternative to `date_diff`, see function `age`.
**Syntax** **Syntax**