Oracle中Trunc和Round--Date Format Models

ROUND and TRUNC Date Functions

Table 7-13 lists the format models you can use with the ROUND and TRUNC date functions and the units to which they round and truncate dates. The default model, 'DD', returns the date rounded or truncated to the day with a time of midnight.

Table 7-13 Date Format Models for the ROUND and TRUNC Date Functions

Format Model	Rounding or Truncating Unit
CC SCC	One greater than the first two digits of a four-digit year
SYYYY YYYY YEAR SYEAR YYY YY Y	Year (rounds up on July 1)
IYYY IY IY I	ISO Year
Q	Quarter (rounds up on the sixteenth day of the second month of the quarter)
MONTH MON MM RM	Month (rounds up on the sixteenth day)
WW	Same day of the week as the first day of the year
IW	Same day of the week as the first day of the ISO year
W	Same day of the week as the first day of the month
DDD DD J	Day
DAY DY D	Starting day of the week
HH HH12 HH24	Hour
MI	Minute

The starting day of the week used by the format models DAY, DY, and D is specified implicitly by the initialization parameter NLS_TERRITORY.