[Solved] How to speed up the SQL query execution time in MySQL database?

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. Prefer Inner Join Over Left Join (modified query below): We identified that one or more left joined entities (e.g. `right_table`) are used in the 'where' clause, in a way that allows to replace it with an optimized inner join. Inner joins can be fully optimized by the database, while Left joins apply limitations on the database's optimizer.
  3. Prefer Sorting/Grouping By The First Table In Join Order (modified query below): The database can use indexes more efficiently when sorting and grouping using columns from the first table in the join order. The first table is determined based on the prediction of the the optimal first table, and is not necessarily the first table shown in the FROM clause.
Optimal indexes for this query:
ALTER TABLE `left_table` ADD INDEX `left_table_idx_right_id_add_time` (`right_table_id`,`add_time`);
ALTER TABLE `right_table` ADD INDEX `right_table_idx_category_id` (`category`,`id`);
The optimized query:
        MAX(left_table.add_time) AS max_add_time 
            ON `left_table`.`right_table_id` = `right_table`.`id` 
        left_table.add_time <= NOW() 
        AND (
                right_table.some_id = 1 
                AND right_table.category != -2
            OR (
                right_table.another_id = 1 
                AND right_table.category != -1
        AND NOT (right_table.category = -3) 
        AND NOT (right_table.category = -4) 
        `max_add_time` DESC,
        `left_table`.`id` DESC LIMIT 12

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* original question posted on StackOverflow here.