How Does MySQL Handle ORDER BY and LIMIT Clauses in SQL Queries?

MySQL's Handling of ORDER BY and LIMIT in SQL Queries

MySQL processes ORDER BY and LIMIT clauses in a specific order within SQL queries. This order significantly impacts the results, especially when both clauses are present.

Consider this query:

<code class="language-sql">SELECT article FROM table1 ORDER BY publish_date LIMIT 20</code>

MySQL's execution steps are:

1. WHERE Clause Execution: Any WHERE clause conditions are evaluated first, filtering the dataset to include only matching rows.
2. ORDER BY Execution: The ORDER BY clause is then applied to the filtered results. This sorts the rows according to the publish_date column (in ascending order by default).
3. LIMIT Execution: Finally, the LIMIT clause restricts the output to the first 20 rows from the already sorted dataset.

In the example, the query retrieves the 20 most recently published articles because the sorting happens before the limiting. This ensures that the top 20 results, based on the publish_date, are returned.

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