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I have the following SQL query:
SELECT * FROM table WHERE field_1 <> field_2
Which is the best index structure to use, to keep this query efficient: two indexes on field_1 and field_2 or a single index which includes both fields?
EDIT: The database is MySQL
If you have a enormous table better is to denormalize it and store the result of filed1<>field2 in separate column, and update it on every insert/update of the corresponding row