auto generated indexes

when viewing a database in the taskpad view from
enterprise manager, i notice there are a lot of indexes on
tables that have been automatically generated. they are
named like _WA_Sys_TransactionID_479C827A (where
TransactionID is a column in the table). Does someone
know where they come from and what they are used for?
There are more than one on some tables.
ThanksMaria
These are not indexes, they are just statistics on columns that are
auto-generated when the optimizer is trying to come up with a plan involving
the columns. Knowing the data distribution in the column can help the
optimizer come up with a better plan. By default, they are created on any
unindexed column used in a query. This is controlled by a database option
'auto create statistics'.
--
HTH
--
Kalen Delaney
SQL Server MVP
www.SolidQualityLearning.com
"Maria" <mariac@.rcspf.co.za> wrote in message
news:2334101c38c21$f4de13b0$a601280a@.phx.gbl...
> when viewing a database in the taskpad view from
> enterprise manager, i notice there are a lot of indexes on
> tables that have been automatically generated. they are
> named like _WA_Sys_TransactionID_479C827A (where
> TransactionID is a column in the table). Does someone
> know where they come from and what they are used for?
> There are more than one on some tables.
> Thanks