ORA-01843 not a valid month- Comparing Dates

Question

I have a problem when try to select data from a table filtering by date.

For example:

SELECT * FROM MYTABLE WHERE MYTABLE.DATEIN = \'23         


        

Answer 1

Just in case this helps, I solved this by checking the server date format:

SELECT * FROM nls_session_parameters WHERE parameter = 'NLS_DATE_FORMAT';

then by using the following comparison (the left field is a date+time):

AND EV_DTTM >= ('01-DEC-16')

I was trying this with TO_DATE but kept getting an error. But when I matched my string with the NLS_DATE_FORMAT and removed TO_DATE, it worked...

Answer 2

You are comparing a date column to a string literal. In such a case, Oracle attempts to convert your literal to a date, using the default date format. It's a bad practice to rely on such a behavior, as this default may change if the DBA changes some configuration, Oracle breaks something in a future revision, etc.

Instead, you should always explicitly convert your literal to a date and state the format you're using:

SELECT * FROM MYTABLE WHERE MYTABLE.DATEIN = TO_DATE('23/04/49','MM/DD/YY');

Answer 3

I know this is a bit late, but I'm having a similar issue. SQL*Plus executes the query successfully, but Oracle SQL Developer shows the ORA-01843: not a valid month error.

SQL*Plus seems to know that the date I'm using is in the valid format, whereas Oracle SQL Developer needs to be told explicitly what format my date is in.

• SQL*Plus statement:

  select count(*) from some_table where DATE_TIME_CREATED < '09-12-23';
  

VS

• Oracle SQL Developer statement:

   select count(*) from some_table where DATE_TIME_CREATED < TO_DATE('09-12-23','RR-MM-DD');
  

Answer 4

If you don't need to check exact timestamp, use

SELECT * FROM MYTABLE WHERE trunc(DATEIN) = TO_DATE('23-04-49','DD-MM-YY');

otherwise, you can use

SELECT * FROM MYTABLE WHERE DATEIN = TO_DATE('23-04-49 20:18:07','DD-MM-YY HH24:MI:SS');

Here, you use hard code date,if you directly compare then you must use DD-MM-YY HH24:MI:SS else you might get ORA-01849: hour must be between 1 and 12.

Answer 5

ALTER session set NLS_LANGUAGE=’AMERICAN’;

Answer 6

If you are using command line tools, then you can also set it in the shell.

On linux, with a sh type shell, you can do for example:

export NLS_TIMESTAMP_FORMAT='DD/MON/RR HH24:MI:SSXFF'

Then you can use the command line tools and it will use the specified format:

/path/to/dbhome_1/bin/sqlldr user/pass@host:port/service control=table.ctl direct=true