DTRUNC: Returning the Start of a Date Period for a Given Date

DTRUNC(date_or_timestamp, date_period)

where:

date_or_timestamp

Date or date-time

Is the date or timestamp of interest, which must provide a full component date.

date_period

Is the period whose starting or ending date you want to find. Can be one of the following:

• DAY, returns the date that represents the input date (truncates the time portion, if there is one).
• YEAR, returns the date of the first day of the year.
• MONTH, returns the date of the first day of the month.
• QUARTER, returns the date of the first day in the quarter.
• WEEK, returns the date that represents the first date of the given week.

  By default, the first day of the week will be Sunday, but this can be changed using the WEEKFIRST parameter.

• YEAR_END, returns the last date of the year.
• QUARTER_END, returns the last date of the quarter.
• MONTH_END, returns the last date of the month.
• WEEK_END, returns the last date of the week.