We can use Sybase Central to easily setup a foreigh key on a child table
whose column value is null.
Howerer we cannot seem to do this with systax. The following statement
results in an error...

ALTER TABLE "dba"."sfdc_tran"
ADD FOREIGN KEY "fk_wrk_machine" ("company_code", "wrk_code",
"wrk_mach_code")
REFERENCES "DBA"."wrk_machine" ("company_code", "wrk_code",
"wrk_mach_code")
ON UPDATE CASCADE

The error is: No primary key value for foreign key 'fk_wrk_machine' in table
'sfdc_tran'

With the Sybase Central FK wizzard we just check the "Allow null values"
checkbox and the fk is created with no errors. How do we duiplicaate this
using syntax?

* None of the columns in either table have a "Unique" constraint.
ASA 8.02

TIA
Mike

I would try to copy and paste the FKey from Sybase Central into you
Text Editor.

HTH
Thomas

Thomas,
I don't find any way to view the syntax of the Foreign Key in Sybase
Central, much less copy it. The graphical representation is there, but no
textual syntax. Am I missing something?

TIA,
Mike

"tduemesnil" <tduemesnil (AT) googlemail (DOT) com> wrote

AFAIK, a null in the child field automatically satisfies a FK
constraint, you don't need to specify "Allow Nulls" in the script.

It's only if you don't want Nulls that you add "NOT NULL"

I don't think it's the Nulls causing the problem, but some other
Not-Null fields that aren't matching and Sybase Central is not
catching.

FYI, if you can perform an "Unload Database", you will be able to see
the script that Sybase creates to re-create your database - this
should show you the appropriate script to create the FK.




On 31 Aug 2009 06:11:22 -0700, "Mike Marston" <mikem (AT) ksitech (DOT) com>
wrote: