How Does MySQL Order Rows When No ORDER BY Clause is Specified?

MySQL Row Ordering for "SELECT * FROM table_name;"

MySQL does not provide any guarantees regarding the order of rows returned in a result set when no ORDER BY clause is specified in a query. The internal implementation details of the database engine determine the order of the returned rows, which may vary depending on factors such as the storage engine used and the specific optimization techniques employed.

In practice, MySQL InnoDB storage engine reads rows from the index used by the query optimizer, so the order of the returned rows depends on that index. When no index is used, rows are read from the clustered index (usually the primary key) and returned in primary key order.

However, relying on the default row order is strongly discouraged. It is recommended to always specify an ORDER BY clause to control the order in which the rows are returned, ensuring consistent and predictable results across different versions of MySQL or even different storage engines.

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