Re: hash join and nested loop join in an oltp query

  • From: Mladen Gogala <mladen@xxxxxxxxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Tue, 4 May 2004 15:04:28 -0400

On 05/04/2004 02:43:13 PM, ryan.gaffuri@xxxxxxx wrote:
> what types of cases make hash joins superior to nested loops? I see them alot 
> in batch processing when I need > to  join most of the rows, but I am see 
> them now when I return a small subset of rows.

Well, if you have to use full table scan to retrieve rows from one of the 
there is a strong probability that hash join will be faster then the nested loop
approach. Of course, there is a slight problem with the word OLTP, because full
table scans are not allowed in OLTP queries.

> has anyone experienced this? 

Mladen Gogala
Oracle DBA

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