Why Should I Avoid Using `SELECT *` in My SQL Queries?

*The Case Against `SELECT ` in SQL**

While delaying optimization is generally good practice, using SELECT * in SQL queries presents several significant drawbacks. Let's examine why explicitly listing columns is preferable.

Profiling Challenges:

SELECT * makes performance profiling difficult. The query retrieves all columns, obscuring potential bottlenecks. Specifying columns allows for targeted optimization, focusing improvements on the crucial data, rather than a blanket approach.

Error Detection and Prevention:

Explicitly naming columns enables the database to detect errors if a referenced column is removed or altered. This prevents application crashes due to missing data.

Enhanced Code Clarity:

Clearly listing columns enhances code readability. The query's purpose becomes immediately apparent, simplifying understanding and debugging, especially in complex, multi-table queries.

Reduced Data Transfer and Processing:

Retrieving only necessary columns minimizes data transferred across the network and processed by the application. This performance boost is especially noticeable with large datasets.

Oracle Database Specific Considerations:

In Oracle, using SELECT * without an index can severely impact performance. The database might resort to full table scans, negating the benefits of indexing because it lacks information on relevant columns.

In Summary:

Although postponing premature optimization is wise, SELECT * introduces several problems: hindered profiling, error susceptibility, poor readability, unnecessary data handling, and potential performance degradation. Specifying columns ensures accuracy, improves performance, and increases maintainability without compromising the principles of effective optimization.

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