> Op 12 okt. 2018, om 11:23 heeft Clemens Ladisch <clem...@ladisch.de> het
> volgende geschreven:
>
> E.Pasma wrote:
>> select group_concat(b) as list
>> from t
>> group by a
>> having count(b=?1)
>> ;
>
> In SQLite, a boolean expression returns 0 when false, and count(0) is 1.
> You have to generate a NULL for failed matches, or use another function
> like sum() or max() that can filter out zeros.
>
Ok, I withdraw my suggestion.
Yours:
select
group_concat(b) as list
from t
where a in (select a
from t
where b = ?1)
group by a;
looks more meanibgful then.
Also, with large amounts of data, and if column b is indexed, it likely becomes
more efficient.
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