Oracleto_date () function usage

In Oracle databases, the Oracleto_date () function is a frequently used function. The following describes the usage of the Oracleto_date () function in detail.

In Oracle databases, the Oracle to_date () function is a commonly used function. The following describes the usage of the Oracle to_date () function in detail.

In Oracle databases, the Oracle to_date () function is a commonly used function. The following describes the usage of the Oracle to_date () function in detail, hoping to enlighten you.

To_date () and 24-hour notation and display of mm minutes:

1. When Oracle's to_date function is used for date conversion, many Java programmers may directly use the format "yyyy-MM-dd HH: mm: ss" for conversion, however, an error occurs in Oracle: "ORA 01810 format code appears twice ".

Select to_date ('1970-01-01 13:14:20 ', 'yyyy-MM-dd HH24: mm: ss') from dual; for example:
The reason is that SQL statements are case-insensitive. MM and mm are considered to be the same format code, so Oracle SQL uses mi instead of minutes.

Select to_date ('1970-01-01 13:14:20 ', 'yyyy-MM-dd HH24: mi: ss') from dual; 2. Another 24-hour format is used to display HH24.
Select to_char (sysdate, 'yyyy-MM-dd HH24: mi: ss') from dual; // mi is minute
Select to_char (sysdate, 'yyyy-MM-dd HH24: mm: ss') from dual; // mm displays the meaning of the to_date parameter in the month oracle.

1. 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 day of 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') the specific usage of from dual is similar to that of to_char above.

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;