MySQL Query Optimization-index application details

Bad SQL query statements can have a serious impact on the operation of the entire application. They not only consume more database time, but also affect other application components.

Like other disciplines, optimizing query performance is largely dependent on developers' intuition. Fortunately, databases like MySQL come with some assistance tools. This article briefly discusses the three tools: Using indexes, analyzing queries using EXPLAIN, and adjusting the internal configuration of MySQL.

MySQL allows you to index database tables so that you can quickly search for records without scanning the entire table at the beginning, which significantly speeds up query. Each table can have up to 16 indexes. In addition, MySQL also supports multiple column indexes and full-text searches.

It is very easy to add an INDEX to a table. You only need to call the create index Command and specify its fields for the INDEX.
List A provides an example:
Copy codeThe Code is as follows:
Mysql> create index idx_username ON users (username );

Here, the username field of the users table is indexed to ensure that the SELECT query statements that reference this field in the WHERE or HAVING clause run faster than those that do not have an index added. You can run the show index Command to check whether the INDEX has been created (List B ).

It is worth noting that:Indexing is like a double-edged sword. Indexing each field of a table is usually unnecessary and may slow down the operation because MySQL has to re-create indexes for these additional tasks every time it inserts or modifies data in the table. On the other hand, it is not a good idea to avoid indexing each field of a table, because the query operation slows down when the record insertion speed is increased. This requires a balance. For example, when designing an index system, it is wise to consider the table's main functions (data repair and editing.