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  1. #1
    Join Date
    Feb 2004
    Posts
    2

    Unanswered: extensible design

    If I were to design a database model that would be extensible, are there any experiences (or pointers to sources of information) ? I am looking for a practice that would easily enable adding fields when they change, still retaining the old data. I heard of something called as evolutionary databases but I do not know if it fits the need.

  2. #2
    Join Date
    Nov 2002
    Posts
    833
    if you follow the design guides for ERM your datamodell will always be extenable
    the preserve data in columns already persistent and you add a no null column you have to shift the table

    insert into table tmp<table> ([column - list] select * from <table>;

    create table <table> ([column - list] ];

    insert into table <table>( [column list]) select tmp<table>[column list], default value for new_col1, default value for new_col2 ... from tmp<table>;

    if nullable columns added

    alter table <table> add <column_name> <col_spec>;

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