Demystifying Oracle Explain Plan: A Comprehensive Guide for Interview Success

In the realm of Oracle database administration and performance tuning, understanding the explain plan is a crucial skill. The explain plan provides invaluable insights into how Oracle executes SQL statements, allowing you to identify potential bottlenecks and optimize query performance. As you prepare for Oracle interviews, mastering the explain plan will undoubtedly give you an edge over other candidates. In this comprehensive guide,

Oracle Performance Tuning – Read and interpret Explain Plan


What is the explain plan function in Oracle?

EXPLAIN PLAN command – This displays an execution plan for a SQL statement without actually executing the statement. V$SQL_PLAN – A dynamic performance view that shows the execution plan for a SQL statement that has been compiled into a cursor and stored in the cursor cache.

What should I look for in an explain plan?

To understand an Explain Plan, one must study key components like access method, filter conditions, join operations, index usage, and cardinality estimates. Access method is important. It shows how Oracle retrieves rows from a table or index, based on the query’s predicates and available statistics.

What is explain the plan in Oracle and how would you decide to optimize the query based on the explain plan output?

Understanding EXPLAIN PLAN. The EXPLAIN PLAN statement displays execution plans chosen by the Oracle optimizer for SELECT , UPDATE , INSERT , and DELETE statements. A statement’s execution plan is the sequence of operations Oracle performs to run the statement. The row source tree is the core of the execution plan.

How do I explain a plan in SQL Developer?

In SQL Developer, you can look at the Explain Plan (or Execution Plan) by going into the Worksheet window (where the SQL query is written). Open your query there, or write the query you want to analyse. Now, click Explain Plan, or press F10. The execution plan is shown in SQL Developer.

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