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Asked: 2026-05-10T17:56:32+00:00

I have two tables containing Tasks and Notes, and want to retrieve a list

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I have two tables containing Tasks and Notes, and want to retrieve a list of tasks with the number of associated notes for each one. These two queries do the job:

select t.TaskId,        (select count(n.TaskNoteId) from TaskNote n where n.TaskId = t.TaskId) 'Notes' from   Task t  -- or select t.TaskId,        count(n.TaskNoteId) 'Notes' from   Task t left join        TaskNote n on     t.TaskId = n.TaskId group by t.TaskId

Is there a difference between them and should I be using one over the other, or are they just two ways of doing the same job? Thanks.

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1 Answer

  1. On small datasets they are wash when it comes to performance. When indexed, the LOJ is a little better.

    I’ve found on large datasets that an inner join (an inner join will work too.) will outperform the subquery by a very large factor (sorry, no numbers).

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