Microsoft Access 2002/2003 References Activex Data Objects

Posted on 2007-10-17
Last Modified: 2008-01-09
Dear Experts,

What is the difference between check the Microsoft Activex Data Objects 2.1 Library VS Microsoft ActiveX Data Objects 2.8 Library?


Antonio Macias
Question by:rebelscum0000
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    Assisted Solution

    by:DatabaseMX (Joe Anderson - Access MVP)
    Basically 2.8 is a new, updated version ... compatible with later versions of Access.

    LVL 21

    Assisted Solution

    LVL 44

    Accepted Solution

    Well ADO 2.8 is the most recent anyway - wouldn't exactly say it's new any more. ;-)
    (It's all "ADO Classic" now).

    FWIW I'll often start a project with the default (2.1) selected until I need something it doesn't offer.
    (It makes it being already present on a target OS that much more likely... however that isn't really a consideration - as I suspect 2.8 has been included since XP...)

    The main difference to my mind came with 2.5 - and you'll want that if you have need of, say, a Stream object - or named params in a command.

    Those aside - you'll find the same fundamental objects present.  (After all - ADO really only consists of the three primary ones :-).
    LVL 75

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    by:DatabaseMX (Joe Anderson - Access MVP)
    ahh ... I meant ... NewER :-)

    my bad
    LVL 75

    Assisted Solution

    by:DatabaseMX (Joe Anderson - Access MVP)

    Whereas that link is sort of cool ... it's a tad outdated .... since DAO (see below) is anything but obsolute :-)
    Obsolete components

    Several components have been completely removed from MDAC by Microsoft and are no longer supported. They are:

        * DAO: DAO, or Data Access Objects were an object oriented interface created by Microsoft which allowed early versions of Microsoft Access and Visual Basic to access the Jet database engine. Later (in version 3.5) it was able to bypass the Jet engine
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    by:DatabaseMX (Joe Anderson - Access MVP)
    Hey Leigh ... while you are here ...
    Question.  I have read this:
    Say you have a (Select) query in design view in the query grid ... 2-3 tables, nothing special.  You make some changes (new fields, sorting, whatever).  According to what I read ... JET optimizes the query - creates the 'plan' when you Save in design view ... against the existing data at that time ... as opposed to ... when you actually Run the query (from say the query grid)  *after* saving it.  In fact, it says that IF .... you Run the query (from the query grid) ... and then Save again ... the plan goes away.

    What is the reality here?

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    Expert Comment

    by:Leigh Purvis
    Hi MX.
    Sorry not gotten to look at this before now... just been pretty busy and don't get over to EE all that often anyway these days.

    IMO saving a querydef definition results only in the SQL being parsed.  If the SQL is valid then it's committed to the definition. (It's here that nasty things can happen to well formatted SQL - especially subqueries).
    Compiling and forming an optimized execution plan occur only when executing the query (that first time).
    Subsequent calls to the query use that plan - until it has cause to be re-compiled (e.g. by editing the query or compacting the database).

    Saving again *might* cause the plan to be removed... if Access perceives that an edit took place (generally you'd want to be pretty specific about this - making an actual edit... even if it's superficial/temporary - but saving again might be interpreted as an edit by Access).
    But only upon executing the query should optimisation and plan saving occur.
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    Expert Comment

    by:DatabaseMX (Joe Anderson - Access MVP)
    Thanks Leigh.  That would be my guess also.  I think this article got it backwards, which prompted this question. My impression has always been that it occurs when 'first' run after an edit/save or compact operation. I don't see how ... until it was run against the current data set any optimization could occur. I will did up that article and review what it said.

    "and don't get over to EE all that often anyway these days."
    np ... more points for me , HA HA :-)  (but PLEASE - stop by when you can!!!)

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