On 9/6/2010 9:10 AM, Thorsten Heymann wrote:
No, I think you misunderstood me. I have these keys (in this example)
- PRIMARY (id)
- UNIQUE (ip_addr)
- UNIQUE (print_name)
And when of of the UNIQUEs is duplicated, I'll wshow user a message WHAT key is
a doublette.
Actually, that was not what you posted above. In your original example
you have one primary key and one unique key. That unique key is based on
the combination of values {`ip_addr`,`print_name`}. This means that all
of these values pairs are unique
'192.168.1.1','queue1'
'192.168.1.1','queue2'
'192.168.2.1','queue1'
'192.168.2.1','queue2'
If I assume that each row was assigned a sequential ID value, then these
are rows 1..4 . If I attempted to modify row 1 like this
UPDATE `device` SET `print_name` = 'queue_2' where ID = 1;
Then I would hit a conflict. The combination of
{ip_addr='192.168.1.1', `print_name='queue2'}
already exists in the row where the ID value is 2.
Even if I parsed the error entire message, it would not tell me which
element of this UNIQUE key I violated, only that the combination already
exists and which constraint is protecting that combination.
--
Shawn Green
MySQL Principal Technical Support Engineer
Oracle USA, Inc.
Office: Blountville, TN
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