[Solved] SQL Query: Need to speed up this query that diffs against two databases

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. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
  2. 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.
  3. Replace In Subquery With Correlated Exists (modified query below): In many cases, an EXISTS subquery with a correlated condition will perform better than a non correlated IN subquery.
Optimal indexes for this query:
ALTER TABLE `frames` ADD INDEX `frames_idx_item_id` (`item_id`);
ALTER TABLE `items` ADD INDEX `items_idx_id` (`id`);
ALTER TABLE `items` ADD INDEX `items_idx_primary_type_id` (`primary_type`,`id`);
The optimized query:
        D.frames f 
        D.items i 
            ON i.id = f.item_id 
        NOT EXISTS (
                D2.frames AS f21 
                D2.items i2 
                    ON i2.id = f21.item_id 
                    i2.primary_type = 'xxx'
                AND (
                    f.item_id = f21.item_id

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* original question posted on StackOverflow here.