Hi Ed,
The Triggers is NOT necessary using
restrictions on FKs....FB does it well...
Ciao

--- In ib-support@y..., "Edson T. Marques" <marques@o...> wrote:
> I use the ER-Win (Interbase Server Style) to model and
> build a simple database that have two tables:
> Tab1 and Tab2 where Tab1 is parent and Tab2 is child.
>
> Tab2 have a foreign key (CodeT1) that references Tab1.
>
>
> The ER-Win generated the following code:
>
> ------------------------------------------------------
> CREATE TABLE Tab1 (
> CodeT1 CHAR(18) NOT NULL,
> Attrib1 CHAR(18)
> );
>
> CREATE UNIQUE INDEX XPKTab1 ON Tab1
> (
> CodeT1
> );
>
> ALTER TABLE Tab1 ADD PRIMARY KEY (ChaveT1);
>
>
> CREATE TABLE Tab2 (
> CodeT2 CHAR(18) NOT NULL,
> CodeT1 CHAR(18) NOT NULL
> );
>
> CREATE UNIQUE INDEX XPKTab2 ON Tab2
> (
> CodeT2
> );
>
> ALTER TABLE Tab2 ADD PRIMARY KEY (CodeT2);
>
> ALTER TABLE Tab2 ADD FOREIGN KEY (CodeT1) REFERENCES Tab1;
>
> CREATE EXCEPTION ERWIN_PARENT_INSERT_RESTRICT 'Cannot INSERT Parent
table because Child table exists.';
> CREATE EXCEPTION ERWIN_PARENT_UPDATE_RESTRICT 'Cannot UPDATE Parent
table because Child table exists.';
> CREATE EXCEPTION ERWIN_PARENT_DELETE_RESTRICT 'Cannot DELETE Parent
table because Child table exists.';
> CREATE EXCEPTION ERWIN_CHILD_INSERT_RESTRICT 'Cannot INSERT Child
table because Parent table does not exist.';
> CREATE EXCEPTION ERWIN_CHILD_UPDATE_RESTRICT 'Cannot UPDATE Child
table because Parent table does not exist.';
> CREATE EXCEPTION ERWIN_CHILD_DELETE_RESTRICT 'Cannot DELETE Child
table because Parent table does not exist.';
>
> CREATE TRIGGER tD_Tab1 FOR Tab1 AFTER DELETE AS
> DECLARE VARIABLE numrows INTEGER;
> BEGIN
> select count(*) from Tab2
> where Tab2.CodeT1 = OLD.CodeT1 into numrows;
> IF (numrows > 0) THEN
> BEGIN
> EXCEPTION ERWIN_PARENT_DELETE_RESTRICT;
> END
> END !!
>
> CREATE TRIGGER tU_Tab1 FOR Tab1 AFTER UPDATE AS
> DECLARE VARIABLE numrows INTEGER;
> BEGIN
> IF (OLD.CodeT1 <> NEW.CodeT1) THEN
> BEGIN
> select count(*) from Tab2
> where Tab2.CodeT1 = OLD.CodeT1 into numrows;
> IF (numrows > 0) THEN
> BEGIN
> EXCEPTION ERWIN_PARENT_UPDATE_RESTRICT;
> END
> END
> END !!
>
> CREATE TRIGGER tI_Tab2 FOR Tab2 AFTER INSERT AS
> DECLARE VARIABLE numrows INTEGER;
> BEGIN
> select count(*) from Tab1
> where NEW.CodeT1 = Tab1.CodeT1 into numrows;
> IF (numrows = 0) THEN
> BEGIN
> EXCEPTION ERWIN_CHILD_INSERT_RESTRICT;
> END
> END !!
>
> CREATE TRIGGER tU_Tab2 FOR Tab2 AFTER UPDATE AS
> DECLARE VARIABLE numrows INTEGER;
> BEGIN
> select count(*) from Tab1
> where NEW.CodeT1 = Tab1.CodeT1 into numrows;
> IF (numrows = 0) THEN
> BEGIN
> EXCEPTION ERWIN_CHILD_UPDATE_RESTRICT;
> END
> END !!
> ---------------------------------------------------------------
>
>
> My question:
>
> Is the triggers generated by ER-Win really necessary?
>
> In the script exists a statement:
> "ALTER TABLE Tab2 ADD FOREIGN KEY (CodeT1) REFERENCES Tab1;"
> that set the field CodeT1 of Tab2 as a foreign key that
> references Tab1. Is it grantting the consistency and integrity of
> my data base or the triggers will be necessary?
>
>
>
> [Non-text portions of this message have been removed]