How Can Indexing Improve Slow MySQL Query Performance?

Optimizing MySQL Queries by Adding Indexes

Adding indexes to MySQL tables can significantly improve performance for specific queries. When a query is executed, the database system searches for a suitable index to use. An index is a data structure that organizes table data, making it easier and faster to find specific rows.

Problem:

A MySQL table with 150,000 rows experiences slow query performance when searching by a field that is not indexed. The EXPLAIN query reveals that no index is being used for the search.

Solution:

To add an index to the product_id field, execute the following command:

ALTER TABLE `table` ADD INDEX `product_id_index` (`product_id`)

This command will create an index on the product_id field, which will improve query performance.

Possible Cause of Slow Performance:

The difference in data types between the indexed id field (INT) and the product_id field (VARCHAR) may have contributed to the slow performance. Comparing integers to strings in MySQL can be inefficient. To mitigate this issue, ensure that the id field is stored as an integer and the product_id field is stored as a string.

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