Question

I am not certain how to do this select. Here is my table structure.

CREATE TABLE `my_table` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `step` int(2) NOT NULL DEFAULT '0',
  `title` varchar(200) NOT NULL,
  `description` text NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 ;

The step column will contain an integer between 0 and 7. I am attempting to count how many records I have in my table for the range of steps 1 through 6. I need the entire range (1 – 6) including where COUNT equals zero. I would like it to return in order — something like this.

+----------+----------+
|   step   |     n    |
+----------+----------+
|   Step 1 |     100  |
+----------+----------+
|   Step 2 |     150  |
+----------+----------+
|   Step 3 |     135  |
+----------+----------+

I was hoping I would not need to define a procedure for this. Is there a simple way of getting what I need?

Answer 1

SELECT
    s.step
  , COALESCE(t.n, 0) AS n
FROM
        ( SELECT 1 AS step UNION ALL
          SELECT 2 UNION ALL
          SELECT 3 UNION ALL
          SELECT 4 UNION ALL
          SELECT 5 UNION ALL
          SELECT 6 
        ) AS s
    LEFT JOIN
        ( SELECT step 
               , COUNT(*) AS n 
          FROM my_table 
          GROUP BY step 
        ) AS t
      ON t.step = s.step
ORDER BY
    s.step ;