li.js_at_neusoft.com (Jinshan Li) wrote in
news:b60ce575.0506081746.4ac5e817_at_posting.google.com:
> Lee Fesperman <firstsql_at_ix.netcom.com> wrote in message
> news:<42A61E2E.21A_at_ix.netcom.com>...
>> Bob Hairgrove wrote:
>> >
>> > On Tue, 07 Jun 2005 19:53:01 GMT, Lee Fesperman
>> > <firstsql_at_ix.netcom.com> wrote:
>> >
>> > >Lastly, when using EXISTS the preferred form for the SELECT clause
>> > >is 'SELECT *'. Unless the optimizer is crazy it should make no
>> > >difference and is clearer.
>> >
>> > In Oracle versions 8 or lower, 'SELECT 1 ...' was also recommended
>> > ... apparently, the server allocated memory for "*" columns or some
>> > such nonsense, requiring it to query the table definition, whereas
>> > with "SELECT 1" (or some other constant such as 'A') the engine
>> > didn't need to touch the table at all.
>>
>> Oh well ... those 'crazy' optimizers ;^) Of course, the other parts
>> of the query would also normally require accessing table definition
>> to some degree.
>>
>> Thanks for sharing.
>
> who can help me to optimize the sql 1?
Any consultant you are willing to pay.
Received on Wed Jun 08 2005 - 22:34:46 CDT
