I am looking for information on program called Q&A. It is an old
program(DOS) and I really need some
Barbare St. Le'ger
1. How are column statistics used?
I've read Inside SQL Server 7.0 several times now and I see the
sentences that talk about column statistics, but I can't figure out how
the optimizer could possibly ever use such statistics. Are they used
only by Query Analyzer and Index Wizard to provide the "advice" that
indexes 'should' be created on certain columns?
2. Is the % index selectivity value a lot lower in 7.0 than it used to
be (didn't it used to be that if an index would return 20% or more of a
table, the optimizer would choose a table scan or another index). Now
it seems that the selectivity is between 1 and 5%.