Why am I receiving an error for TRUNC function?

Question

select TRUNC(TO_DATE('22-AUG-03'), 'YEAR')
from dual;

ORA-01843: not a valid month

1st example -> https://www.techonthenet.com/oracle/functions/trunc_date.php

I know "trunc" function takes in a date and optional fmt parameter. Why am I getting this error?

Answer 1

I don't think the problem is trunc() . I think the problem is the date format. You are safer using the date keyword and an ISO-standard formatted date:

select TRUNC(DATE '2003-08-22', 'YEAR')
from dual;

The interpretation of a date string depends on the internationalization settings for your particular environment. The above does not have that dependency.

Answer 2

Here is a very simple check: IN THE SAME SESSION where your SELECT fails, and WITHOUT you altering the NLS_DATE_FORMAT , see what happens if you run the simpler statement,

SELECT TO_DATE('22-AUG-03') FROM DUAL

You will get the same error - which proves conclusively that it has nothing to do with TRUNC() .

To make everything work exactly as in the tutorial, issue the command

ALTER SESSION SET NLS_DATE_FORMAT = 'dd-MON-yy'

first, before everything else. Note though that formats that have the year as two digits instead of four are a very bad idea in most cases.

Answer 3

似乎您想获取参数中收到的日期的年份。如果您将'22 -AUG-03'作为参数，则将所需的日期格式添加到TO_DATE函数中，然后将其截断：

SELECT TRUNC(TO_DATE('22-AUG-03', 'dd-MON-yy'),'YEAR') FROM DUAL

Answer 4

Use SELECT EXTRACT (YEAR FROM TO_DATE('22-AUG-03', 'dd-MON-yy')) FROM DUAL; to extract year from date.