How to rename a column name or table name in sql

1. You can rename column name as below:
sp_Rename 'tblusers.Name' , 'UserName', 'column'

2. Using below sql statement you can change object name ( table name, stored procedure name..etc)
sp_Rename 'tblusers', 'tblGlobalUsers'

how to delete top n records using sql delete statement?

DELETE top (n) FROM Table1
Note : This statement will work in sql server 2005 and above but for below version use following sql statement

DELETE tbl FROM (Select Top n * FROM Table1 ) tbl