I have a doubt that if my table do n't have any constraint like Primary Key,Foreign key,Unique key etc. then can i create the clustered index on table and clustered index can have the douplicate records ? My 2nd question is where should we exectly use the non clustered index and when it is useful and benificial to create in table? My 3rd question is How can we create the 249 non clustered index in a table .Is it the meaning, Creating the non clustered index on 249 columns ?

Can you anyone help me to remove my confusion in this.