How to Use EXPLAIN Plan in OracleDB?

Introduction

EXPLAIN PLAN is what the Oracle Optimizer is planning to do with the SQL Query, It is not the same as EXECUTION PLAN which is the actual plan that Oracle actually took.

Basic Syntax

EXPLAIN PLAN FOR <SQL TEXT>;

Viewing the plan

SELECT * 
FROM TABLE(DBMS_XPLAN.DISPLAY);

Example

EXPLAIN PLAN FOR
SELECT employee_id, salary
FROM employees
WHERE department_id = 31;

SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);

Conclusion

In conclusion, understanding how to use EXPLAIN PLAN in Oracle is an essential skill for anyone working with databases, especially when performance and scalability matter. It allows developers and DBAs to look beyond the SQL syntax and understand how Oracle actually executes a query. By analyzing execution paths, join methods, and access strategies, you can identify bottlenecks early and make informed optimization decisions.