Indexes on columns

You can create an index for one or more columns in a table. Indexes are required on columns that must be unique and are not specified as primary keys.

In addition, you must add an index on columns that:
  • Are used in joins that are not specified as foreign keys
  • Are frequently used in filter expressions
  • Are frequently used for ordering or grouping
  • Do not involve duplicate keys
  • Are amenable to clustered indexing