This function is used to calculate the date otained through the truncation of a specified date based on a specified datepart.

It truncates the date before the specified datepart and automatically fills the remaining part with the default value. For details, see Example Code.

datetrunc (string date, string datepart)

**Table 1** Parameters
Parameter	Mandatory	Type	Description
date	Yes	DATE or STRING	Start date The following formats are supported: yyyy-mm-dd yyyy-mm-dd hh:mi:ss yyyy-mm-dd hh:mi:ss.ff3
datepart	Yes	STRING	Time unit of the value to be returned This parameter supports the following extended date formats: year, month or mon, day, and hour. YYYY or yyyy indicates the year. MM indicates the month. mm indicates the minute. dd indicates the day. HH indicates the 24-hour clock. hh indicates the 12-hour clock. mi indicates the minute. ss indicates the second. SSS indicates millisecond.

The return value is of the DATE or STRING type.

If the value of date is not of the DATE or STRING type, the error message "data type mismatch" is displayed.
If the value of date is of the DATE or STRING type but is not in one of the supported formats, NULL is returned.
If the value of datepart is NULL, NULL is returned.
If the value of datepart is hour, minute, or second, the date is truncated to the day and returned.

Example static data

The value 2023-01-01 00:00:00 is returned.

select datetrunc('2023-08-14 17:00:00', 'yyyy');

The value 2023-08-01 00:00:00 is returned.

select datetrunc('2023-08-14 17:00:00', 'month');

The value 2023-08-14 is returned.

select datetrunc('2023-08-14 17:00:00', 'DD');

The value 2023-01-01 is returned.

select datetrunc('2023-08-14', 'yyyy');

The value 2023-08-14 is returned.

select datetrunc('2023-08-14 17:00:00', 'HH');

The value NULL is returned.

select datetrunc('2023-08-14', null);