Does SQL Have a Default Sort Order for Query Results?

Default sort order for SQL query results

Many developers believe that SQL has a default sort order for query data, so they omit the ORDER BY clause in the query. While some database management systems (DBMS) may initially default to sorting data in insertion order (FIFO), this is not guaranteed and may change without prior notice.

It is a misunderstanding that DBMS maintains a deterministic order of unmodified data. In practice, the order may vary arbitrarily, especially when using indexes or performing joins. Therefore, the best practice is to always include an ORDER BY clause in queries that require a specific sort order of results.

By explicitly specifying the sort order, you can ensure that results are displayed and processed consistently in the desired order. This practice minimizes unexpected behavior and improves the accuracy and reliability of data operations. It is important to note that even if the table has a clustered index, the sort order of the results is not guaranteed to match the index key order.

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