A Quick Introduction to Oracles Explain Plan

An explain plan in Oracle is a detailed step by step set of instructions that an SQL statement makes in order to run the SQL query. Typically, Oracle will use an optimizer strategy, and will select the explain plan with the lowest cost associated with running it. As a developer, sometimes we might want to view an explain plan to help optimize a query, by modifying our SQL, or adding new indexes to a particular column to help decrease the cost of the best explain plan.

As someone who is not that familiar with explain plans himself, the purpose of the post is to simply introduce the concepts of explain plans, how to run them, and a very quick overview on how to interpret some of the data contained in them.

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