Finding most common words in a column using sqlite?

Question

I have data that looks like this:

            movie_id    comment
            1           tom cruise is great
            1           great action movie
            2           got teary eyed
            2           great cast
            1           tom cruise is hott

I'd like a function that returns the most common words in the comments, based on what movie_id I select. So if I'm querying movie_id=1, I'd get:

            tom, 2
            cruise, 2
            is, 2
            great, 2
            hott, 1
            action, 1
            movie, 1

While if I query movie_id=2, I'd get:

            got, 1
            teary, 1
            eyed, 1
            great, 1
            cast, 1

I saw some solutions using tsql, but I've never used that before and didn't understand the code. Looking for a way to do this in sqlite3.

Answer 1

You can do this with a really ugly query.

select word, count(*) from (
select (case when instr(substr(m.comments, nums.n+1), ' ') then substr(m.comments, nums.n+1)
             else substr(m.comments, nums.n+1, instr(substr(m.comments, nums.n+1), ' ') - 1)
        end) as word
from (select ' '||comments as comments
      from m
     )m cross join
     (select 1 as n union all select 2 union all select 3
     ) nums
where substr(m.comments, nums.n, 1) = ' ' and substr(m.comments, nums.n, 1) <> ' '
) w
group by word
order by count(*) desc

This is untested. The inner query needs a list of numbers (limited to just 3 here; you can see how to add more). It then checks to see if a word starts at position n+1. A word starts after a space, so I put a space at the beginning of the comments.

Then it pulls the word out, for aggregation purposes.