"Invisible" <voi### [at] devnull> wrote in message
news:4891a551$1@news.povray.org...

> I hadn't considered the possibility of the entire table data being in
> the index itself. That would move the tipping point somewhat...
>

Not the entire table, just the columns required by the query in question.
Say the index table has 15 columns and the query that is looking for all
invoice numbers <  999,999,999 needs to return the date, the address and the
customer name, then an index on InvoiceNumber, Date, Address, CustName is
called a covering index, as it covers this particular query.

If an index is not covering, then, as I mentioned before, the tipping point
isn't most of the table (at least for SQL Server), it's somewhere around 1%

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