Indexes
Indexes are almost like an automatic sort built into the column of data in a table. For example, if you have a lastname column indexed, it would be in order, and any new records added would be put in order per the index.
An index can provide for faster access to data in a query as it is already indexed. It is also helpful if you are sorting or searching by two or more columns at a time.
On the negative side, indexes take up disk space, and slow the process when adding, deleting and updating of rows.
Referential Integrity
Referential Integrity is a set of rules within the database between linked tables that helps to keep the database complete and without loose ends or straggling data. No related records can exist without a parent record. In addition, when referential integrity rules are enforced on the link, when you make a change in one table it is updated in the other. Also, if referential integrity is attempted to be enforced and the related fields are not the same type of data, the rule will be rejected and an error message will be displayed.
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