How to Select Rows with the Maximum Value in a Column Using SQL?

SQL Tip: Efficiently filter rows corresponding to the maximum value of a column

In the MySQL database, it is often necessary to extract the row corresponding to the maximum value of a specific column from the record group. This article describes two main methods.

Method 1: Subquery and connection

This method uses a subquery to determine the maximum value in each grouping. The subquery groups the rows by the grouping identifier and returns the maximum value of the specified column. Then, join the results with the main table using the grouping identifier and maximum value as the join condition.

Example:

<code class="language-sql">SELECT a.id, a.rev, a.contents
FROM YourTable a
INNER JOIN (
    SELECT id, MAX(rev) rev
    FROM YourTable
    GROUP BY id
) b ON a.id = b.id AND a.rev = b.rev</code>

Method 2: Self-connection and filtering

Another way is to join the main table with itself using a left outer join. The join condition is applied to the grouping identifier and an additional condition is added to compare the values ​​on the left and right sides of the join. The filter ensures that only rows with no corresponding row on the right (i.e. the row with the largest value) are included in the result.

Example:

<code class="language-sql">SELECT a.*
FROM YourTable a
LEFT OUTER JOIN YourTable b
ON a.id = b.id AND a.rev < b.rev
WHERE b.id IS NULL;</code>

Summary

Both methods give the same results and comply with ANSI SQL standards. They are also relatively performance-friendly, but actual performance will vary depending on the database system, schema design, and presence of indexes. It is recommended to benchmark both approaches to determine the best solution for a specific scenario.

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