is that possible sql keep tracking the time? - sql

Question

I'm a freshman in sql. So that recently my lecture had give us one practical.
The practical file was showing an error.
INSERT INTO sales VALUES ('6380', '1111', '2012-10-01 00:00:00', 2, '30', 'TC7777');
The error was 00:00:00. As my lecture say SQL did not allow this format
So here comes my question:
- Is that possible SQL keep tracking all the time , like the 00:00:00 ?
- And is that SQL are key sensitive , SELECT and select or I should keep the habit that put all in upper case ?

Answer 1

Speaking to Oracle only, the database ALWAYS stores times with date/timestamp values. You just have to properly tell it to do so. In your example, you could say:
INSERT INTO sales
VALUES ('6380', '1111', TO_DATE('2012-10-01 00:00:00','YYYY-MM-DD HH:MI:SS')...
The default format for date values in Oracle is governed by the NLS_DATE_FORMAT system parameter in the database. If you don't explicitly supply date values with the TO_DATE function, Oracle will expect date strings to conform to this format. That's why you're getting an error in your example. Also, if you don't supply a time value, it defaults to 00:00:00.
The same principle applies on output, too. You can accept the default output for a date value by simply selecting the value:
SQL> select sysdate from dual;
SYSDATE
---------
27-JUN-15
SQL>
Or you can format it with TO_CHAR:
SQL> select TO_CHAR(sysdate, 'YYYY-MM-DD HH24:MI:SS') from dual;
TO_CHAR(SYSDATE,'YY
-------------------
2015-06-27 11:10:48
SQL>

Answer 2

Is that possible SQL keep tracking all the time , like the 00:00:00 ?
If your Datatype in SQL table is Date, By default in Oracle, Default format for date is Date only so If you are specifying Time with date while inserting data you get error.
To Insert time with date, you have to convert date format while insert data
TO_DATE('2003/05/03 21:02:44', 'yyyy/mm/dd hh24:mi:ss')
SEE Example
You can change this default date format with
alter session set nls_date_format= your date format here
NLS_DATE_FORMAT Refer Here
is that SQL are key sensitive , SELECT and select or I should keep the
habit that put all in upper case ?
SQL is not case sensitive, you can use either one, UPPER CASE, lower case or even Camel Case. Example :- SELECT or select or even Select. Just for better readability, Prefer to use All keywords in UPPER Case.