Thread: help on delete trigger.

Sundararajan wrote:
> I am developing a db application in postgresql and i need to write a delete
> trigger on one of the tables.
>
> the environment is
>
> table1
>
> field1 varchar(64)
> other fields.
>
> table 2.
>
> field1 varchar(64)
> other fields
>
> I need a delete trigger on the table 1, so that if I delete a row from table
> 1 , the corresponding rows from table 2 should also be deleted.
>
> This is the code I have tried.
>
> DROP FUNCTION ApplicationsDeleteFn();
> CREATE FUNCTION ApplicationsDeleteFn()
> RETURNS OPAQUE
> AS '
>  BEGIN
> delete from ports where appName=OLD.appName;
>  RETURN OLD;
>
>  END;
> '
> LANGUAGE 'plpgsql';
>
> Please help me with this, as my work is time bound.

    I  don't see anything wrong with the trigger you have (except
    that you use appName instead of field1).

    But shouldn't that be a foreign key reference with ON  DELETE
    CASCADE  and ON UPDATE CASCADE in the first place? This would
    automatically delete the referencing rows, so no need  for  a
    custom  trigger. In addition, it'll ensure that you can't get
    entries into ports for non-existent applications at all.


Jan

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