How to set SQL to find records from last sunday to this sunday (1 week)

Question

This is similar to what I have now, which is:

SELECT COUNT(author) FROM `posts` WHERE `date` >= DATE_SUB(CURDATE(), INTERVAL 1 WEEK) AND author='FooBar'

This will give me a count of how many times an author has posted in the past 1 week.

I want to instead have it so if I am to run the program on Sunday at 5:30 PM to look for posts from last Sunday 12:00 AM to this Sunday 12:00 AM. Likewise, if I forget to run it on Sunday and it's monday now. I still want it to run from last Sunday 12:00 AM to the Sunday that just past 12:00 AM

Edit:

I have done what I needed using PHP to form the correct SQL statement, but I am still curious how to do this in just SQL.

<?php
    $dayofweek = strftime("%A",time());
    if($dayofweek == "Sunday") {
        $last_sunday = date('Y-m-d h:i:s',strtotime('Last Sunday'));
        $this_sunday = date('Y-m-d h:i:s',strtotime('Sunday'));
    } else {
        $last_sunday = date('Y-m-d h:i:s',strtotime('Last Sunday',strtotime('Last Sunday')));
        $this_sunday = date('Y-m-d h:i:s',strtotime('Last Sunday'));
    }
    print "last_sunday={$last_sunday}<br>";
    print "this_sunday={$this_sunday}<br>";
    print "SELECT COUNT(author) FROM `posts` WHERE `date` <= '$this_sunday' AND `date` >= '$last_sunday' AND author='FooBar'";
?>

Solution

To get the latest preceding sunday midnight, this should do it. Replace both instances of NOW() with your datetime to check another date.

SELECT DATE_SUB(DATE(NOW()), INTERVAL DAYOFWEEK(NOW())-1 DAY) latest_sun

To get the sunday one week earlier, instead use DAYOFWEEK(NOW())+6 DAY.

EDIT: That'd make your query;

SELECT COUNT(author)
FROM `posts` 
WHERE author='FooBar'
  AND `date` >= DATE_SUB(DATE(NOW()), INTERVAL DAYOFWEEK(NOW())+6 DAY)
  AND `date` <  DATE_SUB(DATE(NOW()), INTERVAL DAYOFWEEK(NOW())-1 DAY)