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Thread: default value for a field

  1. #1
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    default value for a field

    can one use a select statement returning a single value for "default" ? what would be the syntax ? (enclosed, not enclosed ...)
    ex : select max(id) from ids

    Regards

  2. #2
    Lianja Development Team barrymavin's Avatar
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    Seqno() operates in a similar way to AUTOINC and returns a unique row id.
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  3. #3
    Lianja Development Team barrymavin's Avatar
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    I should also mention that this handles concurrent requests while maintaining that the result is guaranteed unique. The original question you asked about using SELECT MAX() ... Is not guaranteed to return a unique id in a multiuser context.
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  4. #4
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    I can't use seqno(), as it is re-initialised at app startup. It has to be a sequence used by surrogate keys. My workaround is a virtual table invoking a function defined on the db side.
    Regards

  5. #5
    Lianja Development Team barrymavin's Avatar
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    Additionally, each row (record) inserted into a Lianja table has a hidden readonly column called SYNCNUM which is used internally, but it can be referenced in your apps too.

    GUID() is another built-in function which can be used to generate a unique id but unlike SEQNO() it's values are in random order whereas SEQNO() is always ascending.
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  6. #6
    Lianja Development Team barrymavin's Avatar
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    The next Seqno() is maintained in the table header. It is not reset at app startup.
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  7. #7
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    you mean in RC8?

  8. #8
    Lianja Development Team barrymavin's Avatar
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    No it is in RC7.
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  9. #9
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    unless I am doing something wrong, seqno() does'nt behave that way
    table structure
    Structure for table : tab.dbf
    Alias : tab
    Number of records : 4
    Date of creation : 08/12/2013
    Date of last update : 08/12/2013
    DES3 Encrypted : No
    CursorAdaptor : No
    Field Field Name Type Width Dec Description
    1 ID Integer 1 id
    2 TSTAMP Character 19 tstamp
    ** Total ** 24
    In form Id is read only, default is seqno()
    below is what i get after creating 2 records, exiting the app and creating 2 other records
    ID TSTAMP

    1 08/12/2013 07:04:42
    2 08/12/2013 07:05:08
    1 08/12/2013 07:06:14
    2 08/12/2013 07:06:21

    4 records selected in 5ms
    Regards

  10. #10
    Lianja Development Team barrymavin's Avatar
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    There seems to be an issue using seqno() with tables opened exclusively. I will look into it and fix it. It works shared.
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