Add 28 to last 2 digit of date and replace the order - mysql

Question

I have a number such as this : 840106
I need to do the following :
Change the number to date add - and flip the number : 06-01-84
add 28 to the last 2 digit that the date will be : 06-01-12
84 + 16 = 00 + 12 = 12
number is always changing sometimes it cab be 850617 , but format is always same add - and add 28 last 2 digit.
any ideas how to help me here ?

Answer 1

Here is a sqlite solution:
create table t( c text);
insert into t (c) values(990831);
insert into t (c) values(840106);
insert into t (c) values(800315);
insert into t (c) values(750527);
insert into t (c) values(700923);
insert into t (c) values(620308);
select c, substr(c,5,2) || '-' || substr(c,3,2) || '-' ||
case when (substr(c,1,2) + 28) < 100 then (substr(c,1,2) + 28)
else case when ((substr(c,1,2) + 28) - 100) < 10 then '0' || ((substr(c,1,2) + 28) - 100)
else ((substr(c,1,2) + 28) - 100)
end
end
from t;

Answer 2

For formatting you can use
http://www.w3schools.com/sql/func_date_format.asp
For adding days to the date you should take a look at date_add() function
mysql> SELECT DATE_ADD('1998-01-02', INTERVAL 31 DAY);
http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_date-add

Answer 3

Assuming date is the name of the column containing your date:
DATE_FORMAT(DATE_ADD(STR_TO_DATE(date, %y%m%d), INTERVAL 28 YEAR), %d-%m-%y);
What this does is first formats the string into a date, then adds 28 years, then converts back to string with the new format.
SQLite is a lot tricker with this, you'll need to use substrings.
substr(date,5) || "-" || substr(date,3,4) || "-" || CAST(CAST(substr(date,1,2) as integer) + 28 - 100) as text
I'm not too experienced with SQLite so the casting may be a bit weird.

Answer 4

Here is a t-sql solution that you can use and migrate to mysql.
declare #myDate as char(8) = '840106';
declare #y as char(2), #m as char(2), #d as char(2);
set #y = LEFT (#myDate, 2);
declare #yi as int = Convert (int, #y);
IF #y between 30 and 99 ----------- pick a cut-off year
SET #yi = (28 - (100-#yi));
SET #y = CONVERT(char, #yi)
set #m = SUBSTRING(#myDate, 3, 2);
set #d = SUBSTRING(#myDate, 5, 2);
SET #myDate = #d + '-' + #m + '-' + #y;
PRINT #myDate;