Why Aren't Database Query Results Ordered Without an 'Order By' Clause?

Understanding Unordered Database Query Results

Many assume database queries return results ordered according to the WHERE clause. This is incorrect. Without an explicit ORDER BY clause, the order of results is undefined.

The database is not obligated to return rows in any particular sequence. The order may vary between query executions.

Consider this example:

<code class="language-sql">SELECT * FROM table_name WHERE field_name IN ('item1', 'item2', 'item3');</code>

The WHERE clause lists items in a specific order, but the output won't necessarily match that order. The database's internal workings determine the result set sequence.

Relational databases lack a default sorting mechanism absent an ORDER BY clause. To guarantee consistent ordering, always include an ORDER BY clause defining the desired sorting criteria.

In short, relying on the order of results without an ORDER BY clause is unreliable. Always explicitly specify the desired sorting using ORDER BY for predictable results.

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