To expand on David's response, SQL Server creates unique indexes to support
PRIMARY KEY and UNIQUE constraints. These can be created as
clustered/non-clustered like regular indexes and SQL Server can use these
for query optimization. UNIQUE constraints may be used instead of unique
indexes. Personally, I always use UNIQUE constraints instead of unique
indexes because uniqueness is a data characteristic.
--
Hope this helps.
Dan Guzman
SQL Server MVP
"Mansoor Azam" <ma******@shoa.net> wrote in message
news:c6************@ID-31123.news.uni-berlin.de...
When I add a unique key constraint to column in SQL 6.5 why does it also
create an index. e.g. In the table subaccounts I added a unique key
constraint for the column login and SQL creates an index with the name
UQ_SubAccounts_2__19 (UKC).
Does this also mean that there is no need to create an index for this
column?
thx
Mansoor