MySql index: How to efficiently use indexes to improve MySQL performance

MySql's index: How to efficiently use indexes to improve MySQL performance

MySql, as an open source relational database management system, is widely used in various Web applications and enterprise information systems. Indexing is an important function in MySql, which can significantly improve the speed of querying data. However, improper use can also lead to performance degradation or even the collapse of the entire system. Therefore, an in-depth understanding and use of MySql indexes is a required course for every developer. This article will introduce MySql indexes and how to efficiently use indexes to improve MySQL performance.

1. What is an index

Simply put, an index is a database object that can improve the access speed of data in a database table. In MySQL, most indexes are implemented based on the B-tree algorithm. B-tree is a balanced search tree that can quickly locate data items stored on disk or in memory. The B-tree data structure has a root node, several intermediate nodes and several leaf nodes. Each node contains multiple elements and pointers to other nodes.

2. MySql index types

MySql supports many different types of indexes, the common ones are as follows:

1. Primary Key Index

Each table can only have one primary key index, which is used to uniquely identify each row of data. Under normal circumstances, the primary key index will be automatically created. If not, it can be added through the ALTER TABLE statement.

2. Unique Index (Unique Index)

The unique index requires that the value in the data column is unique and can include NULL values. If the NOT NULL constraint is not specified, null values ​​are allowed. Unique indexes can also be used to speed up queries on data, but insertions and updates are slower.

3. Normal Index (Normal Index)

Normal index is also called a non-unique index and is the most basic index type. Can be created on columns with or without NULL values, but duplicate index values ​​are ignored.

4. Full-text Index

Full-text index is used to match keywords in natural language. Can only be used on TEXT columns and CHARACTER columns on MyISAM tables and InnoDB tables.

5. Composite Index (Composite Index)

A composite index refers to an index created on multiple columns. It can accelerate joint queries of multiple columns, but it cannot achieve the maximum acceleration effect for single column queries.

3. How to select and create indexes

Indices can improve the execution efficiency of query statements, but too many or too few will affect performance. Therefore, how you select and create indexes is very important.

1. Create only necessary indexes

If the data in the table is small, or the query statement only contains one SELECT statement, then there is no need to create an index. Because the MySql executor directly scans the entire table when querying a smaller table, it is also very fast and does not require additional disk space.

2. Select the most suitable column

Selecting an effective index column is the key to ensuring efficient indexing. Generally speaking, it is more effective to select frequently queried columns or columns that participate in filtering as index columns.

3. Avoid excessive indexing

Indexing requires additional disk space. Too many indexes cause additional overhead and affect the performance of insert, update, and delete operations. Therefore, creating only necessary indexes is the key to improving MySql performance.

4. How to use indexes to optimize query statements

1. Use EXPLAIN to view the query plan

TheExplain command can display the way the MySQL query optimizer executes the query statement. By viewing the results returned by this command, developers can help developers understand how the query optimizer executes query statements, thereby optimizing the query statements.

2. Choose the appropriate index type

Choosing the appropriate index type can greatly improve the execution efficiency of the query statement. In practical applications, the most suitable index type needs to be selected based on the actual situation. For example, when performing fuzzy queries, using full-text indexes can optimize query efficiency.

3. Avoid unnecessary sorting

Sorting operations require a lot of CPU and memory resources, so sorting operations should be avoided as much as possible. Optimization can be achieved through reasonable index design and the use of small limit statements.

4. Avoid full table scans

Full table scans will consume a lot of disk IO and CPU resources, so they should be avoided as much as possible. Optimization can be done by adding indexes, etc.

5. Conclusion

This article introduces the basic concepts of indexes, common index types in MySql and how to select and create indexes. At the same time, it also introduces how to use indexes to optimize query statements and avoid unnecessary sorting and full table scans to improve the performance of MySql. In the actual application process, specific index design and optimization need to be carried out based on the actual situation.

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