Timetable Stats PHP Page

Question

I have a field called dPostTime, which has the date and time stored of an entry.

If I wanted to create a page that showed me the number of entries per hour, would I need to have 24 queries, one for each hour, or what's the best way to do this.

I'd like the chart to appear as follows:

5-6pm - 24 posts
6-7pm - 56 posts
7-8pm - 34 posts
8-9pm - 35 posts

etc......

Thanks!

Answer 1

  SELECT COUNT(*),
         HOUR(`dPostTime`) AS `hr`
    FROM `table`
GROUP BY `hr`

After that in php format hr to be equal 'hr - 1' - hr

Answer 2

MySQL doesn't have recursive functionality, so you're left with using the NUMBERS table trick -

1. Create a table that only holds incrementing numbers - easy to do using an auto_increment:

   DROP TABLE IF EXISTS `example`.`numbers`;
   CREATE TABLE  `example`.`numbers` (
     `id` int(10) unsigned NOT NULL auto_increment,
      PRIMARY KEY  (`id`)
   ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
   

2. Populate the table using:

   INSERT INTO NUMBERS
     (id)
   VALUES
     (NULL)
   

   ...for as many values as you need.

3. Use DATE_ADD to construct a list of dates, increasing the days based on the NUMBERS.id value. Replace "2010-01-01" and "2010-01-02" with your respective start and end dates (but use the same format, YYYY-MM-DD HH:MM:SS) -

   SELECT x.dt
     FROM (SELECT DATE_FORMAT(DATE_ADD('2010-01-01', INTERVAL (n.id - 1) HOUR), '%H:%i') AS dt
             FROM numbers n
            WHERE DATE_ADD('2010-01-01', INTERVAL (n.id - 1) HOUR) <= '2010-01-02' ) x
   

4. LEFT JOIN onto your table of data based on the datetime portion.

      SELECT x.dt,
             COALESCE(COUNT(a.dPostTime), 0) AS numPerHour
        FROM (SELECT DATE_FORMAT(DATE_ADD('2010-01-01', INTERVAL (n.id - 1) HOUR), '%H') AS dt
                FROM numbers n
               WHERE DATE_ADD('2010-01-01', INTERVAL (n.id - 1) HOUR) <= '2010-01-02' ) x x
   LEFT JOIN YOUR_TABLE a ON DATE_FORMAT(a.dPostTime, '%H') = x.dt 
    GROUP BY x.dt
    ORDER BY x.dt
   

Why Numbers, not Dates?

Simple - dates can be generated based on the number, like in the example I provided. It also means using a single table, vs say one per data type.