On 07/08/2011 20:30, Shawn H Corey wrote:
On 11-08-07 03:20 PM, shawn wilson wrote:
It can be sped up (slightly) with an index.
Indexes in SQL don't normally speed up sorting. What they're best at is
selecting a limited number of records, usually less than 10% of the
total. Otherwise, they just get in the way.
The best you can do with a database is to keep the table sorted by the
key most commonly used. This is different than an index. An index is an
additional file that records the keys and the offset to the record in
the table file. The index file is sorted by its key.
Exactly. So to sort a database in the order of its key field all that is
necessary is to read sequentially through the index and pull out the
corresponding record.
I would suggest that the OP could do this 'manually'. i.e. build a
separate index file with just the key fields and pointers into the
primary file. Once that is done the operation is trivial: even more so
if the primary file has fixed-length records (and if not I would like a
word with the person who decided on a 44G file that must be read
sequentially!).
Cheers,
Rob
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