When Should Indexes Be Considered?
Unique indexes are implicitly used in conjunction with a primary key for the primary key to work. Foreign keys are also excellent candidates for an index because they are often used to join the parent table. Most, if not all, columns used for table joins should be indexed.
Columns that are frequently referenced in the ORDER BY and GROUP BY clauses should be considered for indexes. For example, if you are sorting on an individual's name, it would be quite beneficial to have any index on the name column. It renders an automatic alpha-betical order on every name, thus simplifying the actual sort operation and expediting the output results.
Furthermore, indexes should be created on columns with a high number of ...
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