[Solved] PHP/MySQL Subquery returns more than 1 row

How to optimize this SQL query?

In case you have your own slow SQL query, you can optimize it automatically here.

For the query above, the following recommendations will be helpful as part of the SQL tuning process.
You'll find 3 sections below:

  1. Description of the steps you can take to speed up the query.
  2. The optimal indexes for this query, which you can copy and create in your database.
  3. An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
  1. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
  2. Reduce Impact Of Subqueries In Select Clause (modified query below): Subqueries in the SELECT clause will be executed once per each select row. Therefore, reducing the amount of selected rows in the FROM clause before getting to the SELECT clause will result in a performance improvement.
Optimal indexes for this query:
ALTER TABLE `shortlink_analytics` ADD INDEX `shortlink_analytic_idx_shortlink` (`shortlink`);
ALTER TABLE `shortlinks` ADD INDEX `shortlinks_idx_shortlink` (`shortlink`);
The optimized query:
SELECT
        optimizedSub1.*,
        (SELECT
            shortlinks.link 
        FROM
            shortlinks 
        WHERE
            shortlinks.shortlink = optimizedSub1.short) AS shLink 
    FROM
        (SELECT
            shortlink_analytics.shortlink AS short,
            COUNT(shortlink_analytics.shortlink) AS shortcount 
        FROM
            shortlink_analytics 
        JOIN
            shortlinks 
                ON shortlink_analytics.shortlink = shortlinks.shortlink 
        GROUP BY
            shortlink_analytics.shortlink 
        ORDER BY
            COUNT(shortlink_analytics.shortlink) DESC LIMIT 10) AS optimizedSub1

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* original question posted on StackOverflow here.