Oracle to_date usage

Oracle to_date usage
Description of date format parameters
D. day of the week
The name of day, which is filled with spaces to 9 characters.
Day of DD month
The day of the year in DDD
Short Name of Dy day
Week of the Year of the iw iso Standard
Four-digit year of the iyyy ISO Standard
Yyyy four-digit year
Last three digits of YYY, YY, and Y years, two digits, one digit
HH hours, at 12 hours
Hh24 hours, in 24 hours
Mi score
SS seconds
Mm Month
Abbreviated month of Mon
Full name of month
W the week of the month
The week in WW

1. Date interval operation
Current Time minus 7 minutes
Select sysdate, sysdate-interval '7' minute from dual
Current Time minus 7 hours
Select sysdate-interval '7' hour from dual
Current Time minus 7 days
Select sysdate-interval '7' day from dual
Current Time minus July
Select sysdate, sysdate-interval '7' month from dual
Current Time minus 7 years
Select sysdate, sysdate-interval '7' year from dual
Time Interval multiplied by a number
Select sysdate, sysdate-8 * interval '2' hour from dual
2. Date-to-character operations
Select sysdate, to_char (sysdate, 'yyyy-mm-dd hh24: MI: ss') from dual
Select sysdate, to_char (sysdate, 'yyyy-mm-dd hh: MI: ss') from dual
Select sysdate, to_char (sysdate, 'yyyy-DDD hh: MI: ss') from dual
Select sysdate, to_char (sysdate, 'yyyy-mm IW-D hh: MI: ss') from dual
Refer to the Oracle documentation (oracle901doc/server.901/a90125/SQL _elements4.htm #48515)
3. Character-to-date operations
Select to_date ('1970-10-17 21:15:37 ', 'yyyy-mm-dd hh24: MI: ss') from dual
The usage is similar to that of to_char.
4. Use of the trunk/Round Function
Select trunc (sysdate, 'Year') from dual
Select trunc (sysdate) from dual
Select to_char (trunc (sysdate, 'yyyy'), 'yyyy') from dual
5. Oracle has millisecond-level data types
-- Returns the current time year month hour minute second millisecond
Select to_char (current_timestamp (5), 'dd-MON-YYYY hh24: MI: ssxff') from dual;
-- Returns the second millisecond of the current time. The precision after the second can be specified (max = 9)
Select to_char (current_timestamp (9), 'mi: ssxff ') from dual;
6. computing program running time (MS)
Declare
Type RC is ref cursor;
Rochelle RC;
Rochelle dummy all_objects.object_name % type;
Rochelle start number default dbms_utility.get_time;
Begin
For I in 1000
Loop
Open l_rc
'Select object_name from all_objects '|
'Where object_id = '| I;
Fetch l_rc into l_dummy;
Close l_rc;
End loop;
Dbms_output.put_line
(Round (dbms_utility.get_time-l_start)/100, 2) |
'Seconds ...');
End;