How can I display enum string key instead of integer value in SQL query? - sql

Question

I am pretty new to SQL. I assume this is fairly simple, but I haven't been able to find a straightforward answer online.
I am writing a simple SQL query to group database records by an enum column, and display the count of each value. It works fine, but the output is displaying the enum integer, where I want it to display the string key of that enum value.
Here is an example of the SQL query:
SELECT COUNT(a.sound) as "Sound Count", a.sound
FROM animals a
GROUP BY a.sound
Here is the enum definition:
enum sound: {
bark: 0,
meow: 1,
moo: 2
}
And here is the output of the query:
Sound Count Sound
2 0
4 1
3 2
Whereas I really want:
Sound Count Sound
2 bark
4 meow
3 moo

Answer 1

You are asking the DB for info using SQL and so it will not have any knowledge of your Rails enums. You need to use Rails to make the query:
Animals.all.group(:sound).count(:sound)
=> {"bark"=>2, "meow"=>4, "moo"=>3}
For a pure sql answer with Postgresql:
SELECT temp.sound_count,
CASE
when temp.sound = 0 then 'bark'
when temp.sound = 1 then 'meow'
when temp.sound = 2 then 'moo'
END
AS my_sound
FROM (SELECT COUNT(s.sound) as sound_count, a.sound from animals a
GOUP BY a.sound)
AS temp;

Answer 2

If you're not working on a legacy database and are able to change the schema, then I would suggest not using an integer backed enum. Using a string backed enum will make your database readable without the application code. Then when you add new values to your code, you don't need to document what the integers mean.
Instead of defining the enum as you do, define it as strings:
enum sound: {
bark: 'bark',
meow: 'meow',
moo: 'moo'
}
And make sure that the column in the database is also a string.
Now you get all the benefits of enum without the hassle of integers in the database. Your query will also work as-is and produce the result you asked for.
As long as the column is indexed, it's basically just as fast to query as an integer. It will just take a few more bytes of space.
If you want to enforce values on the database level, a postgres enum could also be considered.