Transact-SQL - sub query or left-join?

Question

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. JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

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).