Is ORDER BY RAND() the Best Way to Get Multiple Random Results in MySQL?

Improve the query efficiency of multiple random results in MySQL

ORDER BY RAND() is not the only solution?

Although ORDER BY RAND() is a common way to randomize results in MySQL, it is inefficient when multiple random results are needed. Because this requires sorting the entire result set, it is extremely inefficient for large tables.

More efficient alternatives

In order to optimize such queries, it is recommended to use a more efficient method:

<code class="language-sql">SELECT 
    g.*
FROM
    table g
        JOIN
    (SELECT 
        id
    FROM
        table
    WHERE
        RAND() < p><strong>工作原理</strong></p><p>此优化后的查询使用了以下技术：</p></code>

• Index columns: Queries rely on index columns for efficient lookups.
• Subquery: Subquery calculates the percentage of the result set for randomization.
• Join: A subquery is joined with the main query to filter a subset of results that only need to be sorted.
• Sort by join column: Sort using join columns to avoid randomizing the entire result set.

Advantages of optimization methods

This optimization method has the following advantages:

• Speed: queries execute much faster than ORDER BY RAND(), especially for large result sets.
• Scalability: This method is scalable as it avoids table scans, making it suitable for tables with a large number of rows.
• Flexibility: This technique can be applied to any table with indexed columns.

Limitations

It is important to note that this method may not work in all situations. Complex queries involving multiple joins or WHERE clauses may require more complex subqueries and optimization techniques.

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