Doug McNaught wrote:
> "alex b." <mailinglists1@gmx.de> writes:
>
>
>>CREATE TABLE tmp3 (
>>
>>datname VARCHAR(255),
>>title VARCHAR(100),
>>artist VARCHAR(100),
>>album VARCHAR(100),
>>mp3checksum CHAR(32),
>>CONSTRAINT md5
>> FOREIGN KEY (mp3checksum)
>> REFERENCES tcontent (mp3checksum)
>> ON DELETE CASCADE
>>);
>>
>>NOTICE: CREATE TABLE will create implicit trigger(s) for FOREIGN KEY
>>check(s)
>>ERROR: UNIQUE constraint matching given keys for referenced table
>>"tcontent" not found
>>
>>what am I doing wrong here?
>
>
> Column "mp3checksum" of table "tcontent" needs a UNIQUE
> constraint--does it have one?
no it doesn't - because it is possible that the same exact file might be
existent on multiple CDs...
and therefore "mp3checksum" cannot have a UNIQUE constraint.
am I right?
