Talk:Hash join

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Isn't it the other way around? I believe I've read in a book that hash join goes like that:

...first, a single pass through the file with FEWER records... (partitioning phase) ...second, a single pass through the "other" file... (probing phase)Bold text

Yeah, you are right. I'll make some changes to this when I get some free time (hopefully later tonight). bDerrly 13:03, 10 March 2006 (UTC)[reply]

Fixed this problem (hjzla, March 18). Also added some more info.

The link at the bottom to the PDF file seems to be broken Mbadaire (talk) 22:54, 19 April 2010 (UTC)[reply]

I read this and I don't understand what a hash join is. It needs to be written more clear. ie. I was expecting to see a table structure, SQL, and an explanation why a statement is a hash join:

SELECT * FROM Contract c JOIN ContractType ct ON c.ContractTypeID = ct.ContractTypeID —Preceding unsigned comment added by 204.50.142.43 (talk) 16:10, 14 April 2011 (UTC)[reply]

So fix it. Abolen (talk) 19:32, 14 April 2011 (UTC)[reply]

The "Classic hash join" section states "This algorithm is simple, but it requires that the smaller join relation fits into memory, ..." Shouldn't it be something like "This algorithm is simple, but it can loose its performance benefit if the hash table doesn't fit into memory..."? Randallbsmith (talk) 21:14, 11 August 2011 (UTC)[reply]

Wording in first part[edit]

I find this sentence confusing, and perhaps misleading:

  Hash join is similar to nested loop join but faster than nested loop join and hash join is used for equi join.

It is confusing to say "X is like Y but not" with no real explanation. Furthermore, it is my understanding that a join being an equi-join is a necessary condition for using a Hash join, but never precludes the usage of a nested loop join. Therefore, I propose the sentence be reworded as:

  Hash join is faster than the similar nested loop join, but can only be used for equi-joins.

I feel this wording better explains the relation and conditions - similar, but faster and requires special conditions. — Preceding unsigned comment added by 132.68.43.138 (talk) 11:49, 12 September 2018 (UTC)[reply]