[Solved] MySql Get the \"best\" row in each group, by selection

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.
The optimized query:
SELECT
        * 
    FROM
        Table_A a 
    LEFT JOIN
        Table_B b 
            ON a.r_id = b.r_id 
    ORDER BY
        IF(b.fooData = 'A',
        CAST(result AS DECIMAL (4,
        3)),
        myCastFunction(result)) ASC LIMIT 1

Related Articles



* original question posted on StackOverflow here.