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Message Posted: Thu, 09 Nov 2006 @ 18:26:52 GMT
| Subj: | | Re: Value Ordered NUSI & Regular NUSI on Same Column? |
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| From: | | Dieter Noeth |
David Wellman wrote:
| | I don't think there's any advantage to having both a hash and value ordered NUSI on the same column. | |
| | If a query specifies "WHERE date-column = value" then either type of column will allow the indexed access. So what's the reason for having
both ? | |
Full Ack.
IMHO there's no reason, i usually recommend ORDER BY VALUES if there might be any ranges within WHERE. And even if there's no range, there's no
disadvantage i'm aware of.
And a big plus might be a value-ordered multi-column index:
create index (col1, col2) order by ...(col1);
Now you can use that index similar to a two column B-Tree, all following WHERE-conditions could do an index access:
col1 = x
col1 between x and y
col1 = x and col2 = z
col1 between x and y and col2 = z
Dieter
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