Re: finding columns that have three or fewer distinct characters

Jeff Frost escreveu:
> I've got an interesting one...I'm trying to find columns that have three
> or fewer distinct characters (for example, "aaaaaaaaaa"). Wondering if
> I need to write a function or if someone has an idea how to do it with
> built in functions and/or pattern matching?
>
> I think the thing to do would be to lowercase everything, then remove
> all duplicate chars and spaces, then use length() on that, but it's not
> obvious to me how I might remove the duplicate chars with the pattern
> matching support in the docs.
>

Try:
SELECT
array_to_string(array(
SELECT DISTINCT lower(substr('aabbcdddef AB',i,1))
FROM generate_series(1,length('aabbcdddef AB'))
s(i))
, '');

Osvaldo