Is this true that Update SQL Query is slower because of Clustered index??????
Unlikely. Nonclustered indexes may slow a data modification down, because the change has to be made in multiple places, but that shouldn't be true of a clustered index because it's not a second copy of the data
currently i have cluster index on ID columns which have the primary key
How can i indentify the which column should have the Clustered index???
An identity's usually a fairly good choice for a cluster. It's narrow, unique and can't be changed plus the values for new rows are always higher than old, reducing fragmentation. I can't say if there's a better choice without knowing something about the data and how the table is used.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
We stand on the bridge and no one may pass