[SQL] left join where not null vs. inner join

[Emi Lu]

Two tables, each contains more than hundreds of thousands records. Is 
there any efficiency differences between (1) and (2)?

(1) T1 inner join T2 using (c1, c2)

(2) T1 left join T2 using (c1, c2) where c2 is not null


Thanks,
--
Lu Ying

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