How Can I Speed Up Slow MySQL Queries by Adding Indexes?

Adding Indexes to MySQL Tables

Problem:

Slow performance when querying by a non-indexed field in a large MySQL table.

Explanation:

When querying a database table by a field that is not indexed, MySQL has to perform a full table scan, which can be extremely slow for large tables. Adding an index to the field ensures that MySQL can quickly locate the desired rows without having to scan the entire table.

Solution:

Use the following SQL command to add an index to a field:

ALTER TABLE table_name ADD INDEX index_name (field_name)

Example:

In the example provided, you need to add an index to the product_id field using the following command:

ALTER TABLE table ADD INDEX product_id_index (product_id)

Additional Notes:

• Ensure that the field being indexed has a suitable data type for the purpose. In the example, the id field is an integer (INT), while the product_id field is a string (VARCHAR). For efficient performance, use integers for numeric fields and strings for text fields.
• Remember to remove single quotes surrounding integer values in queries. For example, instead of using product_id = '1', use product_id = 1.

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