trunc function
Applies to: 
Databricks SQL Databricks Runtime
Returns a date with the date truncated to the unit specified by the format model unit.
Syntax
trunc(expr, unit)
Arguments
expr: A DATE expression.unit: A STRING expression specifying how to truncate.
Returns
A DATE.
Notes
fmt must be one of (case-insensitive):
'YEAR','YYYY','YY'- truncate to the first date of the year that the date falls in.'QUARTER'- truncate to the first date of the quarter that the date falls in.'MONTH','MM','MON'- truncate to the first date of the month that the date falls in.'WEEK'- truncate to the Monday of the week that the date falls in.
If fmt is not well-formed the function returns NULL.
Examples
SQL
> SELECT trunc('2019-08-04', 'week');
2019-07-29
> SELECT trunc('2019-08-04', 'quarter');
2019-07-01
> SELECT trunc('2009-02-12', 'MM');
2009-02-01
> SELECT trunc('2015-10-27', 'YEAR');
2015-01-01
-- 'JAHR' is not a recognized unit
> SELECT trunc('2015-10-27', 'JAHR');
NULL