Glenn Marintes wrote:
Thanks...
Now its clearer! :)
That's good :)
I read a little on the net. Although some database systems do support ON
UPDATE CASCADE and it is an optional part of the SQL standard (as Bernt
informed us), there are people that claim this feature should not be
used. Their argument is that a primary key should not change; it should
be constant. If you find the need to change it, it might be that you
have selected the "wrong" candidate key to use as the primary key.
There are no definite rules here of course, but the motivation for this
piece of advice seems to be that changing values of primary keys have
caused a lot of trouble for people, especially since the support for
this in database systems has been limited. This also has impact on
portability, as Bernt mentioned.
--
Kristian
Glenn Marintes wrote:
Hi All,
ij> CREATE TABLE Seal ( sealId BIGINT NOT NULL, sealFilename
VARCHAR(512), sealCode VARCHAR(64) NOT NULL, sealName VARCHAR(256)
NOT NULL, sealGroupFK BIGINT NOT NULL, PRIMARY KEY(sealId), FOREIGN
KEY (sealGroupFK) REFERENCES SealGroup (sealGroupId) ON UPDATE
CASCADE );
ERROR 42X01: Syntax error: Encountered "CASCADE" at line 1, column 256.
What does this error mean? How do we correct it?
Hi Glenn,
I'm not an expert on this, but a look in the reference manual tells me
that you cannot use CASCADE with ON UPDATE.
REFERENCES table-Name [ ( Simple-column-Name [ , Simple-column-Name ]*
) ]
[ ON DELETE {NO ACTION | RESTRICT | CASCADE | SET NULL}]
[ ON UPDATE {NO ACTION | RESTRICT }]
|
[ ON UPDATE {NO ACTION | RESTRICT }] [ ON DELETE
{NO ACTION | RESTRICT | CASCADE | SET NULL}]
As you can see, only NO ACTION or RESTRICT can be used with ON UPDATE.
Maybe someone can elaborate on why this is so?
Is this a piece of missing functionality in Derby?
--
Kristian
