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Please explain relationships. I'm so dumb, I'm sorry.

Discussion in 'Information Technology' started by Crawff, Jul 28, 2006.

  1. Crawff

    Crawff
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    Guest

    I've tried to get to grips with MS Access many times in the past but usually
    end up totally defeated by trying to understand how relationships work. I
    have a go, I read the books but nothing seems to work as it should.

    Now I'm trying to put together an Access database to handle items sold on
    eBay. I've set up four tables focussing on different parts of the sale
    (insertion, bid details, despatch, etc.) and I need to have two fields (item
    and Auction ID) from the first table appear across all four tables, linking
    the information therein. I created fields in all the tables for these two
    important items and tried linking them to the first table.

    In my naivity I thought that if I entered, say, an Auction ID into the first
    table it would them automatically appear in the other three tables when I
    opened them. Not the case - as I discovered.

    What stupid thing am I doing wrong? Am I expecting too much? Have I missed
    something blindingly obvious? Can anyone prevent Access from beating me to a
    bloody pulp once again?

    I'm desperate. I know Access is up to this job but if some kind soul can
    point me in the right direction I'd be enternally grateful.
     
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  3. tina

    tina
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    Guest

    understanding relationships is difficult for most people, so you're not
    alone. but make sure you're not focusing solely on table relationships and
    ignoring normalization principles - the two go together, in building a
    correctly structured relational database. really all you can do is keep
    reading and practicing, until the light bulb comes on. recommend you look at
    the resources at
    http://home.bendbroadband.com/conradsystems/accessjunkie/resources.html,
    beginning with the Database Design 101 and Starting Out links.

    hth


    "Crawff" <Crawff@discussions.microsoft.com> wrote in message
    news:B32AF528-6A7D-4996-B325-2EAF5A8BD623@microsoft.com...
    > I've tried to get to grips with MS Access many times in the past but

    usually
    > end up totally defeated by trying to understand how relationships work. I
    > have a go, I read the books but nothing seems to work as it should.
    >
    > Now I'm trying to put together an Access database to handle items sold on
    > eBay. I've set up four tables focussing on different parts of the sale
    > (insertion, bid details, despatch, etc.) and I need to have two fields

    (item
    > and Auction ID) from the first table appear across all four tables,

    linking
    > the information therein. I created fields in all the tables for these two
    > important items and tried linking them to the first table.
    >
    > In my naivity I thought that if I entered, say, an Auction ID into the

    first
    > table it would them automatically appear in the other three tables when I
    > opened them. Not the case - as I discovered.
    >
    > What stupid thing am I doing wrong? Am I expecting too much? Have I missed
    > something blindingly obvious? Can anyone prevent Access from beating me to

    a
    > bloody pulp once again?
    >
    > I'm desperate. I know Access is up to this job but if some kind soul can
    > point me in the right direction I'd be enternally grateful.
     
  4. John Vinson

    John Vinson
    Expand Collapse
    Guest

    On Wed, 12 Jul 2006 18:14:02 -0700, Crawff
    <Crawff@discussions.microsoft.com> wrote:

    >In my naivity I thought that if I entered, say, an Auction ID into the first
    >table it would them automatically appear in the other three tables when I
    >opened them. Not the case - as I discovered.


    A relationship PREVENTS you from entering invalid data. It does not
    automagically create "dummy" placeholder records in the related tables
    - and it shouldn't.

    What you'll need to do is create the tables with the relationships,
    and THEN use a Form with Subforms to enter the data. A Form would be
    based on the "one" side table, and one or more Subforms on the form
    for the "Many"; the Master Link Field and Child Link Field properties
    of the Subform control will cause the AuctionID and ProductID to be
    automatically filled in *when you create a record on the subform* (not
    before).

    Note that table datasheets are NOT designed for data entry, except in
    really "quick & dirty" work. Forms are the way to go.

    John W. Vinson[MVP]
     
  5. Terry Kreft

    Terry Kreft
    Expand Collapse
    Guest

    When I was on the training course in which I was introduced to normalisation
    and relationships, the trainer told me that normalisation was one of those
    things that when you understood it you couldn't believe how "obvious" it
    was. This turned out to be true.

    You've got to understand normalisation first, this then makes it so that you
    understand Candidate Keys, Primary Keys (PK) and Foreign Keys (FK) and what
    their role is in relationships.

    Once you understand that you'll understand why your question is wrong
    headed.

    Relationships do not cause keys to cascade down from the PK to the FK they
    ensure that where an FK exists a corresponding PK exists.

    In Access you can cause the correct FK to appear in a table by using a form
    to enter details into the table. What you do is create a main/subform form,
    you enter details into the form which is bound to the PK side of the
    relationship and as soon as you start to enter details into the subform
    (which is on the FK side of the relationship) Access will enter the key
    values automatically for you.


    --

    Terry Kreft


    "Crawff" <Crawff@discussions.microsoft.com> wrote in message
    news:B32AF528-6A7D-4996-B325-2EAF5A8BD623@microsoft.com...
    > I've tried to get to grips with MS Access many times in the past but

    usually
    > end up totally defeated by trying to understand how relationships work. I
    > have a go, I read the books but nothing seems to work as it should.
    >
    > Now I'm trying to put together an Access database to handle items sold on
    > eBay. I've set up four tables focussing on different parts of the sale
    > (insertion, bid details, despatch, etc.) and I need to have two fields

    (item
    > and Auction ID) from the first table appear across all four tables,

    linking
    > the information therein. I created fields in all the tables for these two
    > important items and tried linking them to the first table.
    >
    > In my naivity I thought that if I entered, say, an Auction ID into the

    first
    > table it would them automatically appear in the other three tables when I
    > opened them. Not the case - as I discovered.
    >
    > What stupid thing am I doing wrong? Am I expecting too much? Have I missed
    > something blindingly obvious? Can anyone prevent Access from beating me to

    a
    > bloody pulp once again?
    >
    > I'm desperate. I know Access is up to this job but if some kind soul can
    > point me in the right direction I'd be enternally grateful.
     
  6. Rick B

    Rick B
    Expand Collapse
    Guest

    "Crawff" <Crawff@discussions.microsoft.com> wrote in message
    news:B32AF528-6A7D-4996-B325-2EAF5A8BD623@microsoft.com...
    > I've tried to get to grips with MS Access many times in the past but
    > usually
    > end up totally defeated by trying to understand how relationships work. I
    > have a go, I read the books but nothing seems to work as it should.
    >
    > Now I'm trying to put together an Access database to handle items sold on
    > eBay. I've set up four tables focussing on different parts of the sale
    > (insertion, bid details, despatch, etc.) and I need to have two fields
    > (item
    > and Auction ID) from the first table appear across all four tables,
    > linking
    > the information therein. I created fields in all the tables for these two
    > important items and tried linking them to the first table.
    >
    > In my naivity I thought that if I entered, say, an Auction ID into the
    > first
    > table it would them automatically appear in the other three tables when I
    > opened them. Not the case - as I discovered.
    >
    > What stupid thing am I doing wrong? Am I expecting too much? Have I missed
    > something blindingly obvious? Can anyone prevent Access from beating me to
    > a
    > bloody pulp once again?
    >
    > I'm desperate. I know Access is up to this job but if some kind soul can
    > point me in the right direction I'd be enternally grateful.



    Thank you one an all for a) answering my questions so patiently and
    helpfully, and b) making me feel a little less stupid that when I first
    posted this cry for help.

    I will persevere at trying to build my database and come to grips with the
    relational aspects of MS Access.

    Thanks again
     
  7. Jamie Collins

    Jamie Collins
    Expand Collapse
    Guest

    Terry Kreft wrote:
    > Relationships do not cause keys to cascade down from the PK to the FK


    They can be set to do so for DELETE and UPDATE actions but not for
    INSERT actions that the OP seem to be expecting.

    Jamie.

    --
     
  8. Terry Kreft

    Terry Kreft
    Expand Collapse
    Guest

    Thankf for the clarification Jamie, I was too focused when posting to
    properly qualify that statement.

    --

    Terry Kreft


    "Jamie Collins" <jamiecollins@xsmail.com> wrote in message
    news:1152801452.939289.184830@p79g2000cwp.googlegroups.com...
    >
    > Terry Kreft wrote:
    > > Relationships do not cause keys to cascade down from the PK to the FK

    >
    > They can be set to do so for DELETE and UPDATE actions but not for
    > INSERT actions that the OP seem to be expecting.
    >
    > Jamie.
    >
    > --
    >
     

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