Quoting Cal Evans <[EMAIL PROTECTED]>:
> Regular keys are just indexes, not necessarily unique, not necessarily on
> fields that don't accept nulls. Their primary function is to speed up data
> retrieval. Use them sparingly as they can have a negative impact on
> inserting and updating records.
I understand that indexes work so fast because they are usually smaller than the
original table, since they contain on average just 1 column, or at least less
information than the complete table. But how about a table with just 2 columns.
Would an index based on the same 2 columns speed up processing, more specific,
would it speed up a SELECT WHERE (the WHERE clause being related to the index
algoritm)
Thanks, Marco
> ----- Original Message -----
> From: "Marco Bleeker" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Friday, June 22, 2001 9:36 AM
> Subject: KEY and index
>
>
> > Hello, I am learning MySQL and have a question. I know about the
> importance
> > of the PRIMARY KEY statement, but I also see a KEY statement being used
> > when creating a table. Is this just short for PRIMARY KEY, or what's the
> > difference?
> >
> > Second question, when I have a large table, but with only 2 small cells
> per
> > row (2 columns), is it useful to create a PRIMARY KEY, KEY, or INDEX for
> > speed (there is no set relation to another table).
> >
> > Third question, when exactly does MySQL use indexes. Is it used when the
> > indexed column is part of a (SELECT *) WHERE statement, together with a
> > non-indexed column? I just want to check if matching a row is present or
> > not, not actually retrieve information ("WHERE ip='$ip' and
> date>curdate()")
> >
> > Thanks, Marco
> > |
> > | Marco Bleeker, Amsterdam
> > | [EMAIL PROTECTED]
> > | http://www.euronet.nl/users/mbleeker/
> > |
> > | Attachments only after prior notice please.
> > | Don't put me on any kind of mailing list.
> > |
> > | I am now receiving the Snowhite virus 4x a day
> > | - some of you must be infected, please check !
> > | (No, you did not get it from me, I use Eudora)
> > | __@
> > | _`\<,_
> > |__(*)/ (*)________________Ah, op DIE fiets !
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