On Mon, 03 Nov 2008 23:01:34 Dalibor Andzakovic wrote:
> > SELECT * FROM table1 LEFT JOIN table2 ON (table1.productid =
> > table2.productid) WHERE table1.productid = '$id'
> >
> > Will get all the records from table1 and matching fileds from table
> 2. Then
> > in you php code you can do
> >
> > While($row = mysqli_fetch_assoc()){
> > If(sizeof($row['blob'] > 0){
> > // do something with blob
> > }
> > }
> >
> > HTH
> >
> > Dali
>
> Thanks, however is it possible to find out what we need to know about
> the blob
> field (Does it exist and have content?) without actually 'select'ing it
> and
> thus introducing it in to the result set?
>
> I am wondering if this will give optimised performance.
Following code makes kittens cry...
SELECT * FROM table1 LEFT JOIN (SELECT productid, 1 AS gotblob FROM table2
WHERE blob IS NOT NULL) AS sel ON (table1.productid = sel.productid)
And in PHP
While($row = mysqli_fetch_assoc()){
If(row['hasblob'] == 1){
Mysqli_select("SELECT * FROM table2 WHERE productid =
'$row[productid]'");
// etc etc
}
}
I suspect you'd be worse off doing a separate SELECT to fetch the blob field so
do some benchmarks. This is probably a good example of premature
eja^H^H^Hoptimisation
dali
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