Only one index at a time can be used per query, so neither strategy is optimal. You need at look at the queries you intend to run against the system and construct indexes which support them.
- md On Thu, Oct 6, 2011 at 2:35 PM, Neil Tompkins <neil.tompk...@googlemail.com>wrote: > Maybe that was a bad example. If the query was name = 'Red' what index > should I create ? > > Should I create a index of all columns used in each query or have a index > on individual column ? > > > On 6 Oct 2011, at 17:28, Michael Dykman <mdyk...@gmail.com> wrote: > > For the first query, the obvious index on score will give you optimal > results. > > The second query is founded on this phrase: "Like '%Red%' " and no index > will help you there. This is an anti-pattern, I am afraid. The only way > your database can satisfy that expression is to test each and every record > in the that database (the test itself being expensive as infix finding is > iterative). Perhaps you should consider this approach instead: > <http://dev.mysql.com/doc/refman/5.5/en/fulltext-natural-language.html> > http://dev.mysql.com/doc/refman/5.5/en/fulltext-natural-language.html > > On Thu, Oct 6, 2011 at 10:59 AM, Tompkins Neil <<neil.tompk...@googlemail.com> > neil.tompk...@googlemail.com> wrote: > >> Hi, >> >> Can anyone help and offer some advice with regards MySQL indexes. >> Basically >> we have a number of different tables all of which have the obviously >> primary >> keys. We then have some queries using JOIN statements that run slowly >> than >> we wanted. How many indexes are recommended per table ? For example >> should >> I have a index on all fields that will be used in a WHERE statement ? >> Should the indexes be created with multiple fields ? A example of two >> basic queries >> >> SELECT auto_id, name, score >> FROM test_table >> WHERE score > 10 >> ORDER BY score DESC >> >> >> SELECT auto_id, name, score >> FROM test_table >> WHERE score > 10 >> AND name Like '%Red%' >> ORDER BY score DESC >> >> How many indexes should be created for these two queries ? >> >> Thanks, >> Neil >> > > > > -- > - michael dykman > - <mdyk...@gmail.com>mdyk...@gmail.com > > May the Source be with you. > > -- - michael dykman - mdyk...@gmail.com May the Source be with you.
