Question

Let’s say I have a boolean field in a database table and I want to get a tally of how many are 1 and how many are 0. Currently I am doing:

SELECT  'yes' AS result, COUNT( * ) AS num
FROM  `table` 
WHERE field = 1

UNION 

SELECT  'no' AS result, COUNT( * ) AS num
FROM  `table` 
WHERE field =  0;

Is there an easier way to get the result so that even if there are no false values I will still get:

----------
|yes | 3 |
|no  | 0 |
----------

Answer 1

Because there aren’t any existing values for false, if you want to see a summary value for it – you need to LEFT JOIN to a table or derived table/inline view that does. Assuming there’s no TYPE_CODES table to lookup the values, use:

   SELECT x.desc_value AS result,
               COALESCE(COUNT(t.field), 0) AS num
     FROM (SELECT 1 AS value, 'yes' AS desc_value
                UNION ALL
                SELECT 2, 'no') x
LEFT JOIN TABLE t ON t.field = x.value
   GROUP BY x.desc_value