Introduction to the use of Oracle Trunc functions

1.TRUNC (for dates)
The date value that the Trunc function truncates for the specified element.
Its specific syntax format is as follows:
TRUNC (Date[,fmt])
which
Date value
FMT the date format, which is truncated by the specified element format. Ignoring it is truncated by the nearest date.
The following is the use of this function:
TRUNC (To_date (' 24-nov-1999 08:00 pm '), ' dd-mon-yyyy hh:mi am ')
= ' 24-nov-1999 12:00:00 am '
TRUNC (To_date (' 24-nov-1999 08:37 pm ', ' dd-mon-yyyy hh:mi am '), ' hh ') = ' 24-nov-1999 08:00:00 am '
Trunc (sysdate, ' yyyy ')--return to the first day of the year.
Trunc (sysdate, ' mm ')--return to the first day of the month.
Trunc (sysdate, ' d ')--Returns the first day of the current week.
Trunc (sysdate, ' DD ')--return to current month day
2.TRUNC (for number)
The TRUNC function returns the processed value, which works very much like the round function, except that the function does not round the specified decimal number before or after the appropriate rounding selection.
Its specific syntax format is as follows
TRUNC (Number[,decimals])
which
Number to be intercepted
Decimals indicates the number of digits that need to be retained after the decimal point. Optional, ignore it to intercept all the decimal parts
The following is the use of this function:
TRUNC (89.985,2) =89.98
TRUNC (89.985) =89
TRUNC (89.985,-1) =80
Note: The second argument can be a negative number, represented as a portion of the following part of the specified digit to the left of the decimal point, that is, 0. Similar to rounding, for example, 1 is the integer to the very bit, if it is 1, it is rounded to 10 digits, and so on.