Indexing Strategies for Improving Query Performance in MySQL
Jul 04, 2025 am 12:51 AM
To improve MySQL query performance, the key is to use indexes reasonably. First, select the appropriate column to establish an index, and give priority to the commonly used columns in WHERE, JOIN, ORDER BY and GROUP BY to avoid blindly gathering columns with small value ranges; second, use composite index instead of multiple single-column indexes, and note that the query needs to use prefix columns to hit the index; third, avoid full table scanning and unnecessary sorting, ensure that the sorted fields have a suitable index, and avoid SELECT * and LIKE '%xxx'; finally, regularly analyze and maintain the index, check the index usage and optimize through EXPLAIN, information_schema.STATISTICS, performance mode and other tools.
MySQL's query performance depends to a large extent on whether the index is used reasonably. A well-designed indexing strategy can significantly improve query speed, and vice versa may lead to system performance degradation or even crashes. Therefore, if you want to make MySQL query faster, the key is to use the index correctly and well .
The following is a few common perspectives to talk about how to formulate more effective indexing strategies.
Select the appropriate column to create an index
Not all columns are suitable for adding indexes. Generally speaking, the following categories of columns should be given priority:
- Columns that often appear in WHERE clauses
- Columns frequently used in JOIN operations
- Columns involved in ORDER BY and GROUP BY
For example: If you often look up user information based on user_id , it is very necessary to add an index in this field. For columns with very small values ??such as gender and state (such as only "male" and "female"), adding ordinary indexes is not very meaningful.
Tips: Don’t blindly index each column, as the index will take up storage space and affect the writing speed.
Use composite indexes instead of multiple single column indexes
Composite indexes (joint indexes) are usually more efficient than multiple single column indexes when your query criteria contain multiple fields. For example, if you have an order table that is often queried by user_id and status , it would be better to create a composite index like (user_id, status) than to index these two fields separately.
But pay attention to the order of composite indexes:
- Query must use prefix columns to hit the index
- If the query only uses the following column and the previous column is not used, then the index may not take effect
For example:
-- Can hit (user_id, status) SELECT * FROM orders WHERE user_id = 10 AND status = 'paid'; -- It may also hit because the prefix column user_id is used SELECT * FROM orders WHERE user_id = 10; -- Not hit because user_id is skipped SELECT * FROM orders WHERE status = 'paid';
Avoid full table scanning and unnecessary sorting
If the execution plan shows using Using filesort or Using temporary , it means that MySQL is doing additional sorting or Using temporary operations, which is usually one of the performance bottlenecks.
It can be optimized by:
- Make sure there is an appropriate index on the sorting field
- For GROUP BY and DISTINCT operations, try to use overwrite indexes
- Try to avoid SELECT *
Also, be careful not to abuse LIKE '%xxx' such fuzzy match, as it will cause the index to fail. If you really need fuzzy search, you can consider using full-text indexing or other search engines to deal with it.
Regularly analyze and maintain indexes
Indexing is not once and for all. As the data volume grows and the query pattern changes, the original index may no longer be applicable. It is recommended to regularly check and clean invalid or inefficient indexes.
You can view index usage in the following ways:
- Analyze SQL execution plans using
EXPLAIN - Query
information_schema.STATISTICStable to view the index definition - Use Performance Schema or slow query log monitoring index usage
In addition, some tools such as pt-index-usage or sys databases can also help you identify unused indexes.
Basically that's it. Indexing strategies are not complicated to say, but details are easily overlooked in actual applications. The key is to combine business scenarios, continuously test and adjust, and find the best solution for your database.
The above is the detailed content of Indexing Strategies for Improving Query Performance in MySQL. For more information, please follow other related articles on the PHP Chinese website!
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