February 10, 2010 at 10:10 am
Everyone, I've recently become familiar with the 2005 Intersect command as a possible replacement for some inner join statements. I've seen a lot of articles comparing the syntax, but not much comparing the performance.
Are there common situations where one command is generally superior to the other?
February 10, 2010 at 11:19 am
The reason there probably aren't that many articles comparing performance between the two is because they're meant to substitute one for the other. INTERSECT is meant to find the distinct values combining two queries. That's a very different goal than the INNER JOIN which is not finding distinct values, but values that simply match between two tables, derived or otherwise.
As a matter of fact, it's worse than that since the INTERSECT operation requires that the values returned by both queries match in data type, so you couldn't even do a normal INNER JOIN operation between disparate tables using INTERSECT.
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February 10, 2010 at 12:08 pm
as Grant stated the intersect is meanth to compare two sets of data, based on all columns of these sets.
An inner join result set is only based on the matching columns mentioned in the ON clause, but will join both sets at row level (columns of table1 + columns of table2 will make one row).
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