Thanks for the information. One final question in what ways should we use
EXPLAIN EXTENDED statement to help improve our query performance.
On Tue, Oct 11, 2011 at 2:51 PM, Johan De Meersman <vegivamp@stripped>wrote:
> ----- Original Message -----
> > From: "Rik Wasmus" <rik@stripped>
> > Depends on the data and usage, but probably I'd go for a index(a,b) &
> > index(b,a) if reads heavily outnumber writes. As index(a) is covered
> > by index(a,b), and index(b) by index(b,a), we don't need to add those,
> > which saves time on modifications.
> I'm trying to think of a scenario where index(a) would be beneficial in the
> presence of index(a,b). If both are available, and all else being equal,
> it's likely that the parser will pick the simplest index; but I can't see it
> having a major impact.
> Any full prefix of a combined index may be used; so afaik a separate index
> on any full prefix is a waste of diskspace and cycles.
> The net conclusion, Neil, is that you actually have to know what you're
> doing :-) Take the time to read the online documentation on mysql.com,
> it's pretty good.
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