Question

I have a database with 2 fileds a date and a string (there are more fileds but only these to are interesting for this) the string can be empty. Now I want to count how many strings are empty and how many are not.

SELECT 
  `date`, `serial`, count(`serial`) as count 
FROM 
  `updates` 
WHERE 
  `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59' 
GROUP BY 
  `serial`

This is my code at the moment. I don’t really know how to aggregate this in a good way.

Greetings
Alex

// EDIT

As Result I want to have:

2012-11-25    NULL        2452
2012-11-25    NOT NULL    3476

Answer 1

If you want to count nulls strings, and not nulls, you could use this:

SELECT
  `date`,
  count(`serial`) as count_not_nulls,
  count(case when `serial` is null then 1 end) as count_nulls
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59'
GROUP BY `date`

EDIT:

SELECT `date`, 'NOT NULL', count(`serial`) as count
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59'
     AND `serial` is not null
GROUP BY `date`
UNION
SELECT `date`, 'NULL', count(1) as count
FROM `updates`
WHERE `date` BETWEEN '2012-11-25 00:00:00' AND '2012-11-25 23:59:59'
      AND `serial` is null
GROUP BY `date`