Ora-01843 Not a Valid Month- Comparing Dates

How do I fix ORA-01843: not a valid month?

Well, it is quite a bad and extended practice to store DATES as strings, either using varchar2 or char. Anyway, having say that, I think you have a problem with your settings or the way you are constructing your query:

SQL> alter session set nls_date_format='YYYYMMDDHH24MISS' ;

Session altered.

SQL> select to_date('20200726123722') from dual ;

TO_DATE('20200
--------------
20200726123722

SQL> select sysdate from dual ;

SYSDATE
--------------
20200726124622

Besides, as you said, if your data is stored as YYYYMMDDHHMISS, you are applying the wrong date mask YYYY-MM-DD HH24:MI:SS to that char. I would use CAST to define the field as DATE.

Example

SQL> create table my_test ( c1 char(20) ) ;

Table created.

SQL> insert into my_test values ('20200726123722') ;

1 row created.

SQL>  insert into my_test values ('20200725123722') ;

1 row created.

SQL> commit ;

Commit complete.

SQL>  alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';

Session altered.

SQL> select cast(c1 as date) from my_test ;

CAST(C1ASDATE)
-------------------
2020-07-26 12:37:22
2020-07-25 12:37:22

SQL>

Update

If you can't change your NLS Session settings, then you must apply a TO_CHAR to the resulting output. But in your case, you want to operate with dates, so as long as it is a date value you want to operate with, you can forget about the mask.

SQL> col value for a20
SQL> select value from nls_database_parameters where parameter = 'NLS_DATE_FORMAT' ;

VALUE
--------------------
DD-MON-RR

SQL> select cast(to_date('20200725123722','YYYYMMDDHH24MISS') as date) from dual ;

CAST(TO_D
---------
25-JUL-20

SQL> select to_char( cast(to_date('20200725123722','YYYYMMDDHH24MISS') as date) , 'YYYYMMDDHHMISS' ) from dual ;

TO_CHAR(CAST(T
--------------
20200725123722

SQL> select case when cast(to_date('20200725123722','YYYYMMDDHH24MISS') as date)  > sysdate
  2  then 'FALSE'
  3  else
  4  'TRUE'
  5  end as result from dual ;

RESUL
-----
TRUE

SQL>

So, if you want to compare the date to another date, don't use to_char. If you want to show the value in a specific format, when you have no option to change the settings, then use to_char.

ORA-01843: not a valid month when inserting a date

Use TO_DATE('2021/07/02', 'YYYY/MM/DD') to convert your date values to the standard database date format

Replace the above date value as your date columns

Oracle SQL/PL - ORA-01843: not a valid month

What you do need - from my point of view - is not to compare date values to strings.

Presuming that date here actually represent a DATE datatype column (why didn't you post table description?) (as already commented, you can't name a column that way, not unless you enclosed its name into double quotes), then

where date >= '2019-08-31'
      ----    ------------
      DATE     this is a string
    datatype

Use date literal, which always has a DATE keyword and date in format 'yyyy-mm-dd':

where date >= date '2019-08-31'

Or, use to_date function with appropriate format mask:

where date >= to_date('2019-08-31', 'yyyy-mm-dd')

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If date column (wrong name, as we already know) actually contains strings and you hope all of them are following the 'yyyy-mm-dd' format, well, some values don't. Storing dates into varchar2 datatype column is almost always a bad idea. Nobody prevents you from storing e.g. '2019-ac-31' into it, and that isn't a valid date value.

Query with error ORA-01843: not a valid month, with data of type DATE

Introduce date constants using the date keyword and YYYY-MM-DD format:

DATA_EXPORTACAO BETWEEN DATE '2020-09-14' and DATE '2020-09-19'

Note that in Oracle, the DATE data type -- despite its name -- also stores a time component. For this reason, I strongly discourage using BETWEEN. Instead:

DATA_EXPORTACAO >= DATE '2020-09-14' AND
DATA_EXPORTACAO < DATE '2020-09-20'

This works regardless of whether there is a time component.

Oracle SQL TO_TIMESTAMP_TZ Format issue ORA-01843: not a valid month

First, you should fix the data model to store date/time values using the appropriate time stamp which is not a string.

Second, I would return the results using dates:

select trunc(to_date(substr(update, 1, 11), 'DD/MMM/YYYY'), 'MON') as yyyymm,
       count(*)
from t
group by trunc(to_date(substr(update, 1, 11), 'DD/MMM/YYYY'), 'MON');

You can, of course, format the first column however you want using to_char(). However, I want to emphasize that your data and your code should be using dates or timestamps.

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