PHWinfo - Afficher un message

04/10/2007, 15h27

On Oct 4, 3:58 pm, Captain Paralytic <paul_laut...@yahoo.com> wrote:
> Well,
> since your where clause operates on field2 of second_table, could you
> swap the tables round and use an index on field2 to limit the rows to
> be operated on?
>
> As it is, all the rows in main_table have to be read, a JOIN attempted
> into second_table and, if the JOIN is successful, field2 must be
> examined.
Wouldn't this prevent me from using the index on sort_field, though?

04/10/2007, 15h27	#3
nk Messages: n/a Hébergeur:	Re: Speeding up large query On Oct 4, 3:58 pm, Captain Paralytic <paul_laut...@yahoo.com> wrote: > Well, > since your where clause operates on field2 of second_table, could you > swap the tables round and use an index on field2 to limit the rows to > be operated on? > > As it is, all the rows in main_table have to be read, a JOIN attempted > into second_table and, if the JOIN is successful, field2 must be > examined. Wouldn't this prevent me from using the index on sort_field, though?