Not knowing the exact internals of how it works...
Assuming that it works much the same way other RDB's
work in their native GL's (generation languages), the
common practice with a relational database is to define/declare
a "cursor" with the SQL statement executed against the database.
After the cursor is defined/declared, then the next operation
that is performed is a "fetch" where information that is available
by the "cursor" is actually pulled from the database and
somehow used. Specifically *how* I don't know.
I remember years ago when doing COBOL programming, when
dealing with a random access indexed file, what we had to
do to get to the data was to...
open indexedfile-name
start indexedfile-name at a particular key value
if error (the start was bad and you're record pointer was
now at the end of the indexedfile)
go back and get a new key value or end program
if good (read operations can be performed to retrieve a
record)
continue
looping paragraph
(
read recordname next
at end
close indexfile-name
....
....
....
)
This is pretty much the same operation as is done with a
RDB. The open is the database/host/user connection. The
start is the definition/declaration of the cursor, and the
read next's are the fetches that return values to be
processed.
> -----Original Message-----
> From: Stephen Abshire [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, January 09, 2002 12:41 PM
> To: [EMAIL PROTECTED]
> Subject: Re: How Query and Fetch work?
>
>
> I like the explanation using the automobile and key. Very
> good :-) Yet at
> the same time if I understand what effect using the different
> grades of fuel
> in my car will have on its performance, I can optimize how
> the car operates.
> Much like the original question, if I know when MySQL caches
> result sets and
> when it is forced to hit the database again I can optimize
> the performance
> of my application.
>
> Personally, I would like to know the answer to this question
> myself. Anyone
> know the internals?
>
>
> ----Original Message Follows----
> From: Dibo Chen <[EMAIL PROTECTED]>
> To: Alex Shi <[EMAIL PROTECTED]>
> CC: [EMAIL PROTECTED]
> Subject: Re: How Query and Fetch work?
> Date: Wed, 09 Jan 2002 10:45:07 -0600
>
> When you are told to fill in fuel and turn the key to drive, I suppose
> you don't care how the fuel runs the car. Do the same things
> in any lib
> you use, pushing the "buttons" in told order would work.
> Well, you may
> dig deeper if you like since the code is available.
>
> Alex Shi wrote:
> >
> > Yesterday I posted a question yet got response. The question
> > is regarding to how Query works. Now I repost it in a more
> > specific way.
> >
> > I am just wondering how MySQL API functions work. Let's look
> > at following two functions:
> >
> > 1. mysql_query(),
> > 2. mysql_fetch_array()
> >
> > To my understanding, mysql_query() will definately to its job with
> > MySQL server. But how about the latter? Does it just fetch data
> > from client/local buffer, which is previously put in by
> mysql_query(),
> > or still has to goto server side to fetch data?
> >
> > Alex
> >
> >
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