Oracle ( ) vs. ANSI JOIN: Which SQL Join Notation Should You Use?

Oracle ( ) vs. ANSI JOIN Specification: Comprehensive Comparison

In the SQL world, Oracle's traditional plus sign ( ) notation and ANSI standard JOIN notation are both used for combining tables, but their differences deserve careful consideration.

Historical background and usage

The

( ) notation originated in early versions of Oracle, predating the development of the ANSI standard. It continues to be used for backward compatibility. While it is not deprecated, modern SQL coding practices prefer ANSI JOIN syntax because of its wider compatibility and greater readability.

Performance Considerations

Performance benchmarks generally do not show significant differences between the two notations. However, ANSI JOIN syntax is more consistent with other SQL implementations, reducing potential performance differences between different platforms.

Grammar restrictions

The

( ) notation faces certain syntax restrictions:

• It can only appear in a WHERE clause, or in a TABLE clause when a left association is specified.
• It must be applied to all join conditions involving the same table.
• It cannot be combined with any expression in the WHERE clause or with the OR logical operator.

In contrast, ANSI JOIN syntax provides greater flexibility and expressive power, allowing a wider range of join operations.

Oracle’s suggestions

Oracle itself recommends not using ( ) notation in new code and instead recommends using ANSI JOIN syntax. The official SQL Language Reference warns that additional rules and restrictions apply to ( ) notation that may not be immediately apparent when designing queries.

Conclusion

While Oracle's plus sign ( ) notation may still exist in legacy code, its use is discouraged in new development. ANSI JOIN syntax provides a more powerful, forward-compatible, and easier-to-read method for joining operations. By adhering to modern SQL coding standards, you can improve code clarity, performance, and cross-platform compatibility.

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