Re: preserving data after updates

I use a modified form of option 3 with an ON UPDATE RULE.... the update rule
copies the row to an inherited table...

CREATE TABLE dm_user (

id SERIAL NOT NULL PRIMARY KEY,

lu_user_type INTEGER NOT NULL REFERENCES lu_user_type(id),
dm_user_address INTEGER NOT NULL DEFAULT 0,
dm_user_email INTEGER NOT NULL DEFAULT 0,

f_name VARCHAR(50) NOT NULL,
m_name VARCHAR(50) NOT NULL,
l_name VARCHAR(50) NOT NULL,

uname VARCHAR(20) NOT NULL,
upwd VARCHAR(20) NOT NULL,
pwd_change_reqd BOOLEAN DEFAULT FALSE,
login_allowed BOOLEAN DEFAULT TRUE,
lost_passwd BOOLEAN DEFAULT FALSE,

create_dt TIMESTAMP NOT NULL DEFAULT NOW(),
change_dt TIMESTAMP NOT NULL DEFAULT NOW(),
change_id INTEGER NOT NULL DEFAULT 0,
active_flag BOOLEAN NOT NULL DEFAULT TRUE

) WITH OIDS;

CREATE TABLE dm_user_history (

history_id SERIAL NOT NULL PRIMARY KEY,
hist_create_dt TIMESTAMP NOT NULL DEFAULT NOW()

) INHERITS (dm_user);

CREATE RULE dm_user_upd_history AS ON UPDATE TO dm_user DO INSERT INTO
dm_user_history SELECT * FROM dm_user WHERE id = old.id;

CREATE RULE dm_user_nodelete AS ON DELETE TO dm_user DO INSTEAD UPDATE
dm_user SET active_flag = FALSE WHERE id = old.id;

"Scott Frankel" <leknarf(at)pacbell(dot)net> wrote in message
news:bd02bff5561d8b271301ba10bafca105(at)pacbell(dot)net(dot)(dot)(dot)
>
> Is there a canonical form that db schema designers use
> to save changes to the data in their databases?
>
> For example, given a table with rows of data, if I UPDATE
> a field in a row, the previous value is lost. If I wanted to
> track the changes to my data over time, it occurs to me that
> I could,
>
> 1) copy the whole row of data using the new value, thus
> leaving the old row intact in the db for fishing expeditions,
> posterity, &c.
> -- awfully wasteful, especially with binary data
>
> 2) enter a new row that contains only new data fields, requiring
> building a full set of data through heavy lifting and multiple
> queries
> through 'n' number of old rows
> -- overly complex query design probably leading to errors
>
> 3) create a new table that tracks changes
> -- the table is either wide enough to mirror all columns in
> the working table, or uses generic columns and API tricks to
> parse token pair strings, ...
>
> 4) other?
>
> Thanks
> Scott
>
>
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