I want to know (by listeners) when a specific field/column of a row
will be updated before it is done!
I need to know the current/old value and the new (after update) value.
e.g.
CREATE TABLE "SetSet" (
oid INTEGER NOT NULL,
set_value_fk INTEGER NOT NULL,
PRIMARY KEY (oid),
FOREIGN KEY(set_value_fk) REFERENCES "Set_Value" (oid) );
CREATE TABLE "Set_Value" (
oid INTEGER NOT NULL,
PRIMARY KEY (oid)
);
sqlite> SELECT set_value_fk FROM SetSet WHERE oid == 1;
3
sqlite> SELECT oid FROM Set_Value;
1
2
3
If an UPDATE will be done on 'set_value_fk' and its value switch from 3
to 1 I want to know that.
background:
I want to implement a reference counter to know when an instance/row
(many-to-one !) is not referenced any more.
I think using query’s for that would cause to much overhead. I am not
sure where I should call such a is-it-still-referenced-query in my
application without producing to much waiting time for my user. Closing
or opening the application is definitely not the correct place for that.
So I think reference counter would be a nice workaround.
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--
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