Re: Performance difference? : [SELECT ON Merge TableAB] vs [(SELECT ON Table A) UNION (SELECT ON TABLE B) ]

[Gleb Paharenko]

Hello.


I've searched in the archives at:
  http://lists.mysql.com/mysql

but the only thing I've found is that the speed difference is rather low. In my opinion,
using UNION is a more flexible solution.




pow <powster@stripped> wrote:
> Hi everyone,
> Take for example two identical tables A & B, and a MERGE table merging 
> both of them.
> Would there be any performance advantage if  I do a select (with a where 
> criteria on an indexed column) on the MERGE table, as opposed to doing a 
> union of two selects with the same WHERE criteria?
> 
> Many Thanks!
> 


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