Re: Simple Display file problem

["Jake M" <jakeroc@xxxxxxxxx>]

That looks great. So, no declaring, opening and closing cursors? That is
pretty neat.

cheers,

Jake.

On 9/20/06, rob@xxxxxxxxx <rob@xxxxxxxxx> wrote:
> Great points.
>
> One "point of information" though.  It's not
> /Exec Sql Select ItemNumber, ItemDescription From ItemFile Where
> ItemNumber = :Item;
> It's
> Exec Sql Select ItemNumber, ItemDescription From ItemFile Where
> ItemNumber = :Item;
>
> No slash.
>
> Actually it's
> Exec Sql Select ItemDescription into :ItemDescription From ItemFile Where
> ItemNumber = :Item;
> After all, if you already know the item number, why move those bytes
> around again?  And, on a cursorless select you need the into.  But that's
> just details.  Your points are well taken.
>
> Rob Berendt
> --
> Group Dekko Services, LLC
> Dept 01.073
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>
>
>
>
> "Alan Campin" <Alan.Campin@xxxxxxxxxxxxxxxx>
> Sent by: rpg400-l-bounces@xxxxxxxxxxxx
> 09/20/2006 01:49 PM
> Please respond to
> RPG programming on the AS400 / iSeries <rpg400-l@xxxxxxxxxxxx>
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> To
> <rpg400-l@xxxxxxxxxxxx>
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>
> Subject
> Re: Simple Display file problem
>
>
>
>
>
>
> <snip>
> Thanks for that insight. Can SQL be used in free-form in V5R4 without
> the
> use of /EXEC and and /END-EXEC tags in C specs? Or do we still have to
> use
> /EXEC and /END-EXEC but can get rid of the C specs. We are still on V5R3
> and
> will take some time to get there but such things are really good to
> know.
> </snip>
>
> New syntax is
>
> /Exec Sql Select ItemNumber, ItemDescription From ItemFile Where
> ItemNumber = :Item;
>
> No /End-Exec. Just a semi-colon.
>
> Asked my boss to get V5R4 on order.
>
> <snip>
> Yes IBM did give us an easy way create an LF & include only the fields
> you need...
> </snip>
>
> Except the catch. It works and increases performance a lot but if I need
> to bring in five tables into a program, I am going to have to define 5
> different logical views unless I can do some joins. Even having a tool
> to do this, a lot of work and difficult to maintain. I have built system
> using the techniques but a ton of work.
>
> <snip>
> all true Alan. But does a 600 CPW i5 have the horsepower to run pure
> SQL instead of RPG?  My guess is it does not.  Fetching thru an SQL
> cursor must be slower than setll and reade. The mapping of more than a
> few SELECT columns would quickly become more cpu intensive than a byte
> copy into a record format.
> </snip>
>
> Actually the opposite is true.
>
> 1. New SQL I/O system is 5 to 7 times faster than DDS file.
>
> 2. New SQL Index system is 2 to 3 times faster than DDS indexes.
>
> 3. SQL has a new query optimizer that is a lot more efficient.
>
> 4. Reading in only the data you need is always going to be faster than
> reading the entire record. A lot of reasons for this primarily having to
> do with buffers. IBM optimizes the moves but byte moves are just not
> going to be significant. Record I/O is the most expensive thing in the
> system.
>
> 5. The other thing with SQL is that you can read multiple records into
> an array mapped to a user space. You cannot do that with Record I/O. If
> you are reading multiple tables with selects and reading in multiple
> records into a user space, the performance is going to be way faster.
> All the work is going to happen at the machine level. I gave an example
> in a previous post.
>
> In short, what used to be true is just not true anymore and it is only
> going to get better. SQL is present and the future.
>
> The only reason I see to continue a lot of record I/O is severely
> unnormalized databases.
>
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