使用MySQL WHERE子句

Question

I have a query in which I am using a WHERE clause.

My QUERY:

SELECT * FROM notifications WHERE recipient= '".$_SESSION['id']."' AND viewed >  
'".$twoweeksago."' OR viewed IS NULL ORDER BY recieved DESC

Basically, the query selects all rows of data where the recipient is the user logged in and viewed is a date less than two weeks old ($twoweeksago is a variable set in my script). But, the default for the viewed column is 0000-00-00 00:00:00 so I had to use:

OR viewed IS NULL

This creates a problem. I thought it was a condition only applied to the previous condition, which is:

 AND viewed > '".$twoweeksago."'

But, it is actually an OR for the entire WHERE clause and voids all previous conditions. How can I write an OR condition that only affects AND viewed > '".$twoweeksago."'

Thanks!

Answer 1

You should wrap your conditions in a parenthesis like this:

SELECT * FROM notifications WHERE recipient= '".$_SESSION['id']."' AND (viewed > '".$twoweeksago."' OR viewed IS NULL) ORDER BY recieved DESC

This should work.

As a side note, you should remember to not use variables directly from the user, since it can introduce a security breech.