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 <vegiv...@tuxera.be>wrote: > ----- Original Message ----- > > From: "Rik Wasmus" <r...@grib.nl> > > > > 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. > > > -- > Bier met grenadyn > Is als mosterd by den wyn > Sy die't drinkt, is eene kwezel > Hy die't drinkt, is ras een ezel > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: > http://lists.mysql.com/mysql?unsub=neil.tompk...@googlemail.com > >
