Oracle ( ) vs. ANSI JOIN: Is it Time to Ditch the Legacy Notation?

Oracle's ( ) Join Syntax: Should You Migrate to ANSI JOIN?

Oracle's legacy ( ) join syntax, while still functional, is outdated compared to the ANSI standard. New code should favor ANSI JOIN for improved clarity, performance, and adherence to modern coding best practices.

Key Differences Between ( ) and ANSI JOIN:

• Syntax: Oracle's ( ) operator signifies outer joins, appended to the joined table or column. ANSI JOIN uses explicit LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN keywords.
• Limitations: The ( ) notation imposes restrictions absent in ANSI JOIN, particularly concerning multiple outer joins within a single query.

Performance Considerations:

ANSI JOIN generally offers superior performance, especially in complex queries. Its clear join specifications facilitate optimal query plan generation by the Oracle optimizer.

Oracle's Recommendation:

Oracle strongly discourages the use of ( ) notation in new development. Migrating to ANSI JOIN ensures better performance and code maintainability.

Illustrative Example:

Here's an Oracle ( ) join:

<code class="language-sql">SELECT * FROM employees e
LEFT JOIN departments d ON e.department_id = d.department_id(+)</code>

Its ANSI equivalent:

<code class="language-sql">SELECT * FROM employees e
LEFT OUTER JOIN departments d ON e.department_id = d.department_id</code>

In this case, the ( ) is redundant. The ANSI version clearly defines the outer join, leading to better readability and performance. Adopting ANSI JOIN is the recommended approach for improved code quality and efficiency.

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