The concept of index
(1) It is a sorted data structure, helping mysql quickly query and update data in database tables
(2) There is no need to scan the entire table, you can find the required data through the physical address
(3) Data structures established for the values of certain fields to improve the search efficiency of the table; not all fields need to create indexes
In MySQL, you can use the ALTER TABLE statement to add an index to a table. Indexing can improve query performance. Here are some common ways to add indexes:
1. Add a normal index (INDEX)
grammar:
ALTER TABLE table_name ADD INDEX index_name(column_list);
For example, add a normal index to the username field of a table named users:
ALTER TABLE users ADD INDEX idx_username(username);
2. Add a unique index (UNIQUE INDEX)
Make sure that the index column's value is unique.
grammar:
ALTER TABLE table_name ADD UNIQUE INDEX index_name(column_list);
For example, add a unique index to the email field of the users table:
ALTER TABLE users ADD UNIQUE INDEX idx_email(email);
3. Add primary key index (PRIMARY KEY)
A table can only have one primary key index, which is used to uniquely identify each row in the table. If no primary key is defined in the table, you can add it using ALTER TABLE.
grammar:
ALTER TABLE table_name ADD PRIMARY KEY(column_list);
For example, add a primary key index to the id field of the users table:
ALTER TABLE users ADD PRIMARY KEY(id);
4. Add full text index (FULLTEXT INDEX)
Used to search for full text types of columns.
grammar:
ALTER TABLE table_name ADD FULLTEXT INDEX index_name(column_list);
For example, add a full text index to the content field of the articles table:
ALTER TABLE articles ADD FULLTEXT INDEX idx_content(content);
When adding an index, the following points need to be considered:
- The index takes up additional storage space.
- Too many indexes may degrade the performance of data insertion, update, and delete.
- Select the appropriate index type and column according to the actual query requirements.
This is the end of this article about several implementation methods for adding indexes to mysql tables. For more information about adding indexes to mysql tables, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!