sql - Difference between NOT IN and equals vs. IN and not equals -


my query needs return usage records pipeline rate not 'no usage'.

what's difference between not exists vs. not in vs. left join null?

i have seen above question , decided use in on exists values in tables nullable. 1 of following better , more efficient or there other way more efficient following two?

select *   usagerecords ur  ur.usagerateid not in (select id                                 pipelinerate pr                                pr.name = 'no usage')  select *   usagerecords ur  ur.usagerateid in (select id                             pipelinerate pr                            pr.name <> 'no usage')

not in going give wrong results if id nullable (which hope not, otherwise has terrible name).

why choose in on exists when has been proven time , time again exists more efficient (or @ least no less efficient), since can short-circuit? in has materialize entire set.

select * -- stop doing   dbo.usagerecords ur   exists   (     select 1 dbo.pipelinerate pr       pr.id = ur.usagerateid       , pr.name <> 'no usage'   );

you can express other query this:

select * -- again, stop doing   dbo.usagerecords ur   not exists    (     select 1 dbo.pipelinerate pr       pr.id = ur.usagerateid       , pr.name = 'no usage'   );

but have no idea which, if either, gets correct results. why typically ask sample data , desired results.

your use of select * have greater negative impact on performance whether use in or exists. fwiw.


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