ora-01858 error with to_date in regexp_replace - oracle11g

Question

I have several rows in my table like below:
row1: abc changed on 12 November, 2008 11:30 AM and its abc..region1
row2: defg updated 14 January, 2012 08:20 PM ......region2
row3: ghijkl corrected by 18 august, 2013 9:30 AM ..something..region3
My requirement is as follows:
All the above dates are in EST time zone and date format is exactly as above and does not change.
I want to update the dates in these rows from EST to different time zones as per the region in that row, and the format should be changed to something like 12 dec 2016 7:30 AM.
So the query I framed is (taking row1 as example) as below:
select regexp_replace(
'abc changed on 12 November, 2008 11:30 AM and its abc..region1',
'([0-9]{2})([[:blank:]]) (January|February|March|April|May|June|July|August|September|October|November|December)(,[[:blank:]])([0-9]{4})([[:blank:]])([0-9]{2}:[0-9]{2})([[:blank:]])(AM|PM)','\1-\3-\5 \7 \9',1,0,'i')
output:
abc changed on 12-November-2008 11:30 AM and its abc..region1
So I am happy with the above query till now because I get a string
with the formatted date. Even though this is not the final date
format, I can use this date to pass to some function which converts
this date according to the region do some processing and fianlly
return a date type.For the same purpose I add to_date in the above
query:
select regexp_replace(
'abc changed on 12 November, 2008 11:30 AM and its abc..region1',
'([0-9]{2})([[:blank:]]) (January|February|March|April|May|June|July|August|September|October|November|December)(,[[:blank:]])([0-9]{4})([[:blank:]])([0-9]{2}:[0-9]{2})([[:blank:]])(AM|PM)',
substr('\1-\3-\5 \7 \9',1),
1,0,'i')
output:
abc changed on 12-November-2008 11:30 AM and its
abc..region1 --> works fine till here
Now I am adding to_date to convert the date string type to real date
type to do some processing on it:
select regexp_replace(
'abc changed on 12 November, 2008 11:30 AM and its abc..region1',
'([0-9]{2})([[:blank:]]) (January|February|March|April|May|June|July|August|September|October|November|December)(,[[:blank:]])([0-9]{4})([[:blank:]])([0-9]{2}:[0-9]{2})([[:blank:]])(AM|PM)',
to_date(substr('\1-\3-\5 \7 \9',1),'dd-mon-yyyy HH:MI AM'),
1,0,'i')
This query is giving me an error:
ORA-01858: a non-numeric character found where a numeric was expected
I checked whether wrong parameters were being passed to
to_date(), and fired the query below, but it worked fine.
Select to_date('12-November-2008 11:30 AM','dd-mon-yyyy HH:MI AM')
from dual;
output:
12-Nov-2008
(I am not worried with the timestamp because itnternall it will be anyways in this date)
To avoid confusion I have numbered the substrings of the regular expression above:
([0-9]{2})-->1 ([[:blank:]])-->2
(January|February|March|April|May|June|July|August|September|October|November|December)-->3
(,[[:blank:]])-->4 ([0-9]{4})-->5 ([[:blank:]])-->6
([0-9]{2}:[0-9]{2})-->7 ([[:blank:]])-->8 (AM|PM)-->9
select regexp_replace(
'abc changed on 12 November, 2008 11:30 AM and its abc..region1',
'([0-9]{2})([[:blank:]]) (January|February|March|April|May|June|July|August|September|October|November|December)(,[[:blank:]])([0-9]{4})([[:blank:]])([0-9]{2}:[0-9]
{2})([[:blank:]])(AM|PM)','\1-\3-\5 \7 \9',1,0,'i')

Answer 1

Assuming your string always has the date in it in that particular format (and that there are no invalid dates etc etc) then the following should work for you:
WITH sample_data AS (SELECT ' the date is 12 November, 2008 11:30 AM' str FROM dual UNION ALL
SELECT 'Here''s a date of 1 March, 2015 1:43 pm' str FROM dual UNION ALL
SELECT '1 February,2016 9:43 AM' str FROM dual UNION ALL
SELECT 'And again it''s 21 May, 2016 9:43 AM and a little bit extra' str FROM dual)
SELECT str,
to_date(regexp_replace(str, '^.*?([[:digit:]]{1,2} [[:alpha:]]{3,9}, ?[[:digit:]]{4} [[:digit:]]{1,2}\:[[:digit:]]{2} (A|P)M).*$', '\1', 1, 1, 'i'), 'dd Month yyyy, hh:mi am') dt
FROM sample_data;
STR DT
---------------------------------------------------------- -------------------
the date is 12 November, 2008 11:30 AM 12/11/2008 11:30:00
Here's a date of 1 March, 2015 1:43 pm 01/03/2015 13:43:00
1 February,2016 9:43 AM 01/02/2016 09:43:00
And again it's 21 May, 2016 9:43 AM and a little bit extra 21/05/2016 09:43:00
The regular expression can be broken down as follows:
^.*? - match any character (except new line) from the start of the line as few times as possible, which may be 0 or more.
([[:digit:]]{1,2} [[:alpha:]]{3,9}, ?[[:digit:]]{4} [[:digit:]]{1,2}\:[[:digit:]]{2} (A|P)M) - this is the pattern we're looking for, and which we'll use to replace the whole string with (this is aliased as \1, which we can then pass into the replace string parameter).
.*$ - match any character up to the end of the string
The second part of the pattern can be further broken down as:
[[:digit:]]{1,2} - one or two digits
- a single space character
[[:alpha:]]{3,9} - three to nine letters (upper or lower case)
, ? - a comma followed by 0 or 1 spaces
[[:digit:]]{4} - four digits
- a single space character
[[:digit:]]{1,2} - one or two digits
\: - a single colon character
[[:digit:]]{1,2} - two digits
- a single space character
(A|P)M - either the letter A or P followed by an M
This should do the trick for you:
WITH sample_data AS (SELECT 'abc changed on 12 November, 2008 11:30 AM and its abc..region1' str FROM dual UNION ALL
SELECT 'defg updated 14 January, 2012 08:20 PM ......region2' str FROM dual UNION ALL
SELECT 'ghijkl corrected by 18 august, 2013 9:30 AM ..something..region3' str FROM dual)
SELECT str,
regexp_replace(str,
'(^.*?)(([[:digit:]]{1,2}) (January|February|March|April|May|June|July|August|September|October|November|December), (?[[:digit:]]{4} [[:digit:]]{1,2}\:[[:digit:]]{2} (A|P)M))(.*$)',
'\1\3-\4-\5\7', 1, 1, 'i') dt
FROM sample_data;
STR DT
------------------------------------------------------------------- --------------------------------------------------------------------------------
abc changed on 12 November, 2008 11:30 AM and its abc..region1 abc changed on 12-November-2008 11:30 AM and its abc..region1
defg updated 14 January, 2012 08:20 PM ......region2 defg updated 14-January-2012 08:20 PM ......region2
ghijkl corrected by 18 august, 2013 9:30 AM ..something..region3 ghijkl corrected by 18-august-2013 9:30 AM ..something..region3