Oracle common index creation method

1. Create a default index:
    CREATE INDEX mycolumn_index ON mytable (myclumn) 
    --eg: CREATE INDEX createpsn_index ON ncrcustommade (createpsn)    
    -- the column name is createpsn
2. Drop the index: DROP INDEX mytable.mycolumn_index
3. Create a clustered index: CREATE CLUSTERED INDEX mycolumn_clust_index ON mytable(mycolumn)
4. Create an index for duplicate records: CREATE CLUSTERED INDEX mycolumn_cindex ON mytable(mycolumn) WITH ALLOW_DUP_ROW
5. Create a unique index: CREATE UNIQUE COUSTERED INDEX myclumn_cindex ON mytable(mycolumn)
6. Create a composite index: CREATE INDEX name_index ON username(firstname,lastname)