Front page | perl.dbi.dev |
Postings from August 2002
>> I have never yet needed to know how many rows were affected
>> by any insert/update, and I don't expect I ever will, unless
>> I were to see a good example of when it's really useful.
>>
>> -- Joe
>>
>
>Here's an example of where it is useful (not that there
>aren't other good ways to do this ).
>
>I have a table with primary key K, and other
>columns C1,...,Cn.
>
>I have the tuple (k,c1,...,cn) that I want to add to
>the table, i.e if the key k already exists in the table
>I want to update the row, otherwise I want to add the
>new row.
>
>Here's how to do it:
>
> $my @parms = (c1,...,cn,k);
> $rows = $db->do("update table set C1=? .... CN=?
> where K=?", undef, @parms);
> if ($rows == 0) {
> # i guess key wasn't there
> $db->do("insert into table (C1,...,Cn,K)
> values (?,...,?,?)", @parms);
> }
>
>otherwise I have to do a select first, and then
>an update or an insert, or do the insert and
>watch for an error and then go ahead and do the
>update -- a little more complicated.
Also error-prone, if your transaction isolation level
allows someone to insert the key between your check and
your insert.
I have used this trick with the row count, too.
-John
Thread Previous
|
Thread Next