SQL date Statement - sql

Question

I need some help figuring out and SQL Statement.
I know what I want I just cant express it.
Im using php, so it doesnt need to be exclusivly SQL, its to act as a filter.
Pseudo code
$query="SELECT * FROM MyTable WHERE 'TIS' is not older than 2 days or empty = ''$ORDER"; }
TIS in the name of the column in my table were I store dates in this format 03-12-09 (d,m,y).
The $ORDER is for ordering the values based on values from other fields not dates.
Im looking at
SELECT *
FROM orders
WHERE day_of_order >
(SELECT DATEADD(day,-30, (SELECT MAX(day_of_order) FROM orders)) AS "-30 Days");
But i dont quite think im on the rigth track with this.
Thanks

Answer 1

Try the following:
SELECT *
FROM MyTable
WHERE COALESCE(TIS, SYSDATE) > SYSDATE - INTERVAL '2' DAY
$ORDER
I don't know what database you're using - the above uses Oracle's method of dealing with time intervals. If you're using SQL Server the following should be close:
SELECT *
FROM MyTable
WHERE COALESCE(TIS, GETDATE()) > DATEADD(Day, -2, GETDATE())
$ORDER
In MySQL try this:
SELECT *
FROM MyTable
WHERE COALESCE(TIS, NOW()) > DATE_SUB(NOW(), INTERVAL 2 DAYS)
$ORDER
I hope this helps.

Answer 2

So, I was pretty lost in all this.
How did it got solved:
First I understood that the Statement I was using was not supported by MySql thanks to eligthment from Bob Jarvis.
_ Second In a comment by vincebowdren wich "strongly" adviced me to change the data type on that field to Date wich indeed I had not, it was a string.
It was pretty Dumb for me to try using SQL operations for Dates on a field that had String values.
So I just RTFM: http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html
and:
mysql> SELECT something FROM tbl_name
-> WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= date_col;
Then proceeded to change the field value to date.
and this is my perfectly working query:
$query="SELECT * FROM MyTable WHERE DATE_SUB(CURDATE(),INTERVAL 2 DAY) <= TIS OR TIS = 0000-00-00 $ORDER "; }
I would like to thank the posters for their aid.