Varchar m/d/yyyy to yyyy/mm/dd sql - sql

Question

I have a file that inputs data in the format m/d/yyyy or m/dd/yyyy depending on whether or not the date value is 2 digits (example 4/1/2015 or 4/14/2015). I need to convert this to a date with the format yyyy/mm/dd (example 2015/04/01 or 2015/04/14). I have tried multiple way but I get the error "Invalid date" every time. Please help.
Things I have tried:
cast((CASE WHEN CHAR_LENGTH(RSA_dt) <10 THEN 0 || TRIM(RSA_dt) end) AS DATE)
CAST( CAST( RSA_dt AS DATE FORMAT 'DD-MMM-YY') AS DATE FORMAT 'YYYY-MM-DD')
cast(RSA_dt as date format 'YYYY-MM-DD')

Answer 1

Which tool do you use for loading?
The easiest way to load this data is to define that column as a VARDATE in a TPT job:
VARDATE(10) FORMATIN 'MM/DD/YY' FORMATOUT 'YYYY-MM-DD'
Otherwise you got a problem as Teradata's CAST doesn't like single digit day/month. Starting with TD14 there's Oracle's TO_DATE, which still doesn't like a single digit month, but at least tolerates single digit day:
TO_DATE(CASE
WHEN RSA_dt LIKE '_/%'
THEN '0' || RSA_dt
ELSE RSA_dt
END
,'mm/dd/yyyy')

Answer 2

This will work for TPT.
Select '1/1/2014' as date1,
TO_DATE (
case
when strtok(date1, '/', 1) between 1 and 9 and strtok(date1, '/', 2) between 1 and 9 then strtok(date1,'/', 3)||'/0'||strtok(date1, '/', 1)||'/0'||strtok(date1,'/', 2)
when strtok(date1, '/', 1) between 1 and 9 and strtok(date1, '/', 2) > 9 then strtok(date1,'/', 3)||'/0'||strtok(date1, '/', 1)||'/'||strtok(date1,'/', 2)
when strtok(date1, '/', 1) > 9 and strtok(date1, '/', 2) between 1 and 9 then strtok(date1,'/', 3)||'/'||strtok(date1, '/', 1)||'/0'||strtok(date1,'/', 2)
else strtok(date1, '/', 3)||'/'||strtok(date1, '/', 1)||'/'||strtok(date1,'/', 2)
end , 'YYYY/MM/DD') as req_date

Answer 3

Here's another solution. It uses a regular expression to add a leading zero to any single-digit number, then standard casting to convert it to a date using existing format, then back to standard format. I have included several examples:
SELECT CAST(CAST(TD_SYSFNLIB.REGEXP_REPLACE('4/1/2015','(?<!\d)(\d)(?!\d)','0\1',1,0,'i') AS DATE FORMAT 'MM/DD/YYYY') AS DATE FORMAT 'YYYY-MM-DD');
SELECT CAST(CAST(TD_SYSFNLIB.REGEXP_REPLACE('4/14/2015','(?<!\d)(\d)(?!\d)','0\1',1,0,'i') AS DATE FORMAT 'MM/DD/YYYY') AS DATE FORMAT 'YYYY-MM-DD');
SELECT CAST(CAST(TD_SYSFNLIB.REGEXP_REPLACE('12/1/2015','(?<!\d)(\d)(?!\d)','0\1',1,0,'i') AS DATE FORMAT 'MM/DD/YYYY') AS DATE FORMAT 'YYYY-MM-DD');

Answer 4

It looks like you're providing the format you want, instead of the format you've got. Try this instead:
cast(RSA_dt as date format 'MM/DD/YYYY')

Answer 5

If you aren't using TPT, then you're stuck playing some awful substring games.
SELECT
SUBSTR(chardate,INSTR(chardate,'/',1,2)+ 1,4) AS theYear,
'00' || SUBSTR(chardate,1,INSTR(chardate,'1',1,1)-2) AS theMonth,
'00' || SUBSTR(chardate,INSTR(chardate,'/',1,1)+ 1,INSTR(chardate,'/',1,2) - INSTR(chardate,'/',1,1)-1) AS theDate,
CAST (theYear || '-' || SUBSTRING(theMonth,LENGTH(theMonth) -1,2) || '-' || SUBSTR(theDate,LENGTH(thedate)-1,2) AS DATE) AS ItsADate
FROM
<yourtable>
Really ugly, but it should work.

Answer 6

This should work.
Select '1/2/2014' as date1,
TO_CHAR(TO_DATE (
case
when strtok(date1, '/', 2) between 1 and 9 then strtok(date1,'/', 3)||'/0'||strtok(date1, '/', 1)||'/'||strtok(date1,'/', 2)
else strtok(date1, '/', 3)||'/'||strtok(date1, '/', 1)||'/'||strtok(date1,'/', 2)
end , 'YYYY/MM/DD'), 'YYYY/MM/DD') as "YYYY/MM/DD"

Answer 7

This will work, though not pretty. Specifically converting M/D/YYYY to YYYYMMDD
select substr(YOURDATE,-4,4) ||
substr('00'||SUBSTR(YOURDATE,1,to_number(regexp_instr(YOURDATE,'\/'))-1),-2,2) ||
case when substr(YOURDATE,2,1) = '/' then
case when substr(YOURDATE,4,1) = '/' then
'0' || substr(YOURDATE,3,1)
else substr(YOURDATE,3,2)
end
else case when substr(YOURDATE,5,1) = '/' then
'0' || substr(YOURDATE,4,1)
else substr(YOURDATE,4,2)
end
end as NEWDATE
from YOURTABLE