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:
- 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:
- Avoid Calling Functions With Indexed Columns (query line: 17): When a function is used directly on an indexed column, the database's optimizer won’t be able to use the index. For example, if the column `Date_Entered` is indexed, the index won’t be used as it’s wrapped with the function `MONTH`. If you can’t find an alternative condition that won’t use a function call, a possible solution is to store the required value in a new indexed column.
- Avoid Calling Functions With Indexed Columns (query line: 17): When a function is used directly on an indexed column, the database's optimizer won’t be able to use the index. For example, if the column `Date_Entered` is indexed, the index won’t be used as it’s wrapped with the function `YEAR`. If you can’t find an alternative condition that won’t use a function call, a possible solution is to store the required value in a new indexed column.
- 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.
- 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.
Optimal indexes for this query:
CREATE INDEX tb_targets_idx_staff ON tb_staff_targets (staff);
The optimized query:
SELECT
CAST(MONTH(s.Date_Entered) AS VARCHAR (2)) + '-' + CAST(YEAR(s.Date_Entered) AS VARCHAR (4)) AS Month,
s.staff,
CASE
WHEN COUNT(*) > 0 THEN COUNT(*)
ELSE 0 END AS Jobs,
ot.monthly_target AS Target
FROM
tb_statistics AS s
LEFT JOIN
tb_staff_targets AS ot
ON (
s.staff = ot.staff
)
GROUP BY
s.staff,
CAST(MONTH(s.Date_Entered) AS VARCHAR (2)) + '-' + CAST(YEAR(s.Date_Entered) AS VARCHAR (4)),
ot.monthly_target