Conditions Based On Inequalities Can’t Use Indexes – How To Resolve?

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Conditions based on inequalities (!=, <>) cannot make use of index(es). I will illustrate this limitation and show you how to optimize SQL statements hitting it.

For the demonstration, I have  a table  students table having a column named result that  can contain the values – ‘Pass’, ‘Fail’, ‘To be evaluated’. The column is characterized by a very non-uniform distribution having most of the rows have the value set to Passed (P). Here’s the (more...)