on 2014 Aug 13 6:12 AM
Two tables:
A (col1, col2, col3, primary key (col1, col2))
B (col1, col2, col3, col4, col5, primary key (col1, col2))
With table B having thousands of records, which of the following statements would be the least expensive?
Option 1:
insert into A (col1, col2, col3) on existing skip
select col1, col2, col3 from B
Option 2:
insert into A (col1,col2,col3)
select col1, col2, col3 from B
where not exists (select * from A where col1=b.col1 and col2=b.col2)
My gut tells me they're exactly the same. But I need more than my gut to go on.
Having said that, my guess is they will have the same plans and the same performance. I am VERY PROUD of my guesswork...
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