Mysql date interval - mysql

Question

I am trying to select rows which are within a certain time period:
$sql = mysql_query(" SELECT * FROM table WHERE ... AND
date BETWEEN ('$date' - Interval 2 YEAR) AND ('$date' + Interval 2 YEAR)
OR date ISNULL");
The format of the dates saved in this column are mm/dd/yyyy
a. how do I select the time interval? currently it is selecting all the rows, not just those within this date range.
b. Am I using the corret syntax to make sure we include all null options as well?
Update.
Following the answers and comments I changed the column type to "Date" (it was varchar), and have also changed the current type of the existing entries to the correct date format.
I now have 2 questions:
a. This is still not working... What else might be the problem?
b. I want to change in PHP where the entry is saved. How ahould I go about this? Is the following correct:
$new_date = mysql_query("STR_TO_DATE($old_date_string,'%m/%d/%Y')");
Solution.
First, I changed the column type to DATE (from VARCHAR).
Second, I moved and converted all the existing entries from their existing column and type (str) to new type (date) and new column.
Third, I added parentheses to the "date" section.
Fourth, I changed ISNULL to IS NULL - addin a space, which changes it from a function to a statement.
Fifth, I am now updating my script so that in the future dates will be saved to the new column in the new type, converting them to the correct fprmat before saving them to the database.
Thankyou #nnicholas and everybody.

Answer 1

If you are really storing your dates as strings I suggest you update your table with something like the following -
-- add a new column of type DATE
ALTER TABLE `table` ADD COLUMN `date_new` DATE AFTER `date`;
-- populate the new column from the old one
UPDATE `table` SET `date_new` = STR_TO_DATE(`date`,'%m/%d/%Y');
-- drop the old column
ALTER TABLE `table` DROP COLUMN `date`;
-- rename the new column
ALTER TABLE `table` CHANGE `date_new` `date` DATE;
After making these changes handling dates will be much easier for you. When inserting the dates that you are receiving you simply use STR_TO_DATE('new_value','%m/%d/%Y') to convert the date during the insert -
mysql_query("INSERT INTO `table` (field1, field2, `date`)
VALUES('value1', 'value2', STR_TO_DATE('$old_date_string','%m/%d/%Y')");
This assumes that $old_date_string has already been sanitised.
With your table structure updated the standard date arithmetic functions will work as intended.
$sql = mysql_query("SELECT *
FROM table
WHERE ...
AND (`date` BETWEEN ('$date' - INTERVAL 2 YEAR) AND ('$date' + INTERVAL 2 YEAR) OR `date` IS NULL)");
$date must be in Y-m-d format.

Answer 2

You can't do date comparisons on it if it's not stored in the database as a date.
You could do something very ugly casting it to a date with STR_TO_DATE() and then comparing but I'd suggest reworking your table structure to store this date as a DATE object.
SELECT * FROM table WHERE ... AND
STR_TO_DATE(date, '%m/%d/%Y') BETWEEN ('$date' - Interval 2 YEAR) AND ('$date' + Interval 2 YEAR)
OR date ISNULL
This assumes that $date is in the correct MySQL DATE format of 2012-03-14 (for 14th March 2012)

Answer 3

You have to CAST/CONVERT your date field that you are getting from MySQL (you really called a date field 'date'? that's a bad idea).
The best answer is to convert your date column to an actual DATE type. You should also not really use the mm/dd/yyyy format as its ambiguous.

Answer 4

You need to enclose the entire date checking part in brackets, like so:
$sql = mysql_query(" SELECT * FROM table WHERE ... AND
(
date BETWEEN ('$date' - Interval 2 YEAR) AND ('$date' + Interval 2 YEAR)
OR date ISNULL
)");
And it should work as expected.
Apart from the missing brackets, your condition seems to take into account NULLs all right (i.e. NULLs would be included in the output regardless of the argument passed).
UPDATE
It seems I was mistaken in presuming that the date column was the date type. #James C has got the point, as well as #nnichols, and their suggestion about changing the column type seems the way to go in your situation.