sqlchanakya (2/19/2011)
Sorry for the incorrect usage "Issue" . I meant, if we are adding ROWID to eliminate the uquifier in the non clustered index(because of non uniqueness in clusterd index), the size of the b tree and leaf level again would increase. So I would like to know that how come making a clustered index unique would be beneficial (offcourse 4 byte uquifier can be replaced with 8 byte ROWID(4 byte is still excess.).
The guideline for a clustered index is narrow AND unique. If you can't make the chosen clustering key unique without making it wide, then stick with a non-unique cluster or find another location for the clustered index or make it wide and accept the effects.
These are guidelines, not hard rules that must be followed. Just understand what it is that you're trading off if you chose one over the other
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability