For the query above, the following recommendations will be helpful as part of the SQL tuning process. You'll find 3 sections below:
Description of the steps you can take to speed up the query.
The optimal indexes for this query, which you can copy and create in your database.
An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
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.
Explicitly ORDER BY After GROUP BY (modified query below): By default, the database sorts all 'GROUP BY col1, col2, ...' queries as if you specified 'ORDER BY col1, col2, ...' in the query as well. If a query includes a GROUP BY clause but you want to avoid the overhead of sorting the result, you can suppress sorting by specifying 'ORDER BY NULL'.
Index Function Calls Using Generated Columns (modified query below): When a function is used directly on an indexed column, the database's optimizer won’t be able to use the index to optimize the search. Creating and indexing a generated column (supported in MySQL 5.7) will allow MySQL to optimize the search.
Remove Redundant Left Joins (modified query below): Redundant LEFT JOINs (e.g. `invoice`) were detected in the query. Removing them will result in a performance improvement. In some cases, JOINs become redundant after an optimization is applied, such as when converting OR conditions to a UNION clause.
Optimal indexes for this query:
ALTER TABLE `invoice` ADD INDEX `invoice_idx_postdate` (`postdate`);
ALTER TABLE `invoice` ADD INDEX `invoice_idx_date_postdate` (`date_postdate`);
The optimized query:
SQL_CACHE date(todaydata.postdate) AS postdate,
WHEN todaydata.amount > 0 THEN todaydata.amount
ELSE 0 END) AS INFLOW,
WHEN todaydata.amount < 0 THEN todaydata.amount
ELSE 0 END) AS OUTFLOW
invoice AS todaydata
todaydata.postdate BETWEEN now() - INTERVAL 2 month AND now() + INTERVAL 1 month