what is the difference between mysql storage engines

The difference between mysql storage engines: 1. MyISAM does not support transactions and row-level locks, while InnoDB supports transactions and row-level locks; 2. InnoDB supports MVCC and foreign keys, while MyISAM does not Supports MVCC and foreign keys.

The operating environment of this tutorial: windows10 system, mysql8.0.22 version, Dell G3 computer.

What is the difference between mysql storage engines

• InnoDB supports transactions while MyISAM does not support transactions

• InnoDB supports Row-level locks, while MyISAM supports table-level locks

• InnoDB supports MVCC, but MyISAM does not support it

• InnoDB supports foreign keys, while MyISAM does not Supports the three storage engines of myisam, innodb and memory in

1. Differences:

1) MyISAM manages non-transaction tables. Provides high-speed storage and retrieval, as well as full-text search capabilities. MyISAM is supported in all MySQL configurations and is the default storage engine unless MySQL is configured to use another engine by default.

2) MEMORY storage engine provides "in-memory" tables. The MERGE storage engine allows collections to be processed on the same MyISAM table as a single table. Just like MyISAM, the MEMORY and MERGE storage engines handle non-transactional tables, and both engines are included in MySQL by default.

Note: The MEMORY storage engine is officially identified as the HEAP engine.

3) InnoDB and storage engines provide transaction security tables, which are included in all MySQL 5.1 binary distributions by default. You can configure MySQL to allow or disable either engine according to your preferences.

2. Introduction to function points

1) MyISAM storage engine

MyISAM storage engine does not It supports transactions, does not support row-level locks, and only supports concurrently inserted table locks. It is mainly used for high-load select.

Myisam type tables support three different storage structures: static, dynamic, and compressed.

(1) Static type: The size of the defined table column is fixed (that is, it does not contain variable-length data types such as xblob, xtext, varchar, etc.), so that mysql will automatically use the static myisam format.

The performance of tables using static formats is relatively high because the overhead required to store data in a predetermined format during maintenance and access is very low. But this high performance comes in exchange for space, because it is fixed when it is defined, so no matter how big the value in the column is, the maximum value will prevail and occupy the entire space.

(2) Dynamic type: If a column (even if there is only one column) is defined as dynamic (xblob, xtext, varchar and other data types), then myisam will automatically use the dynamic type, although the dynamic type table occupies It takes less space than a static table, but it reduces performance, because if the content of a field changes, its position is likely to need to be moved, which will lead to fragmentation. As the data changes more, fragmentation will increase, and data access performance will decrease accordingly.

(3) Compressed type: If a table created in this database is read-only during the entire life cycle, in this case, myisam's compressed table is used to reduce space usage.

2) MEMORY storage engine:

(1) The memory storage engine is a little different from some of the previous storage engines. It uses the data stored in it. to create the table, and all data is also stored in memory.

(2) Each table based on the memory storage engine actually corresponds to a disk file. The file name and table name of the file are the same, and the type is .frm. This file only stores the structure of the table, and its data files are stored in memory, which is conducive to rapid processing of data and improves the processing capabilities of the entire table.

(3) The memory storage engine uses hash (HASH) index by default, which is faster than using B-Tree. If readers want to use B-Tree, they can reference it when creating.

(4) The memory storage engine file data is stored in the memory. If an exception occurs in the mysqld process, the data will disappear if the machine is restarted or shut down. Therefore, the life cycle of tables in the memory storage engine is very short and is generally only used once.

3) innoDB storage engine:

(1) innodb storage engine This mysql table provides transaction, rollback and system crash repair capabilities and multi-version burst control Transaction security.

(2) innodb supports auto-increment columns (auto_increment). The value of an auto-increment column cannot be empty. If it is empty when used, how can the existing value be automatically saved and start to increase in value? If there is but If it is larger than the current value, this value will be saved.

(3) The innodb storage engine supports foreign keys. The table where the foreign key is located is called the child table and the table it depends on is called the parent table.

(4) The most important thing about the innodb storage engine is that it supports transactions and transaction-related functions.

(5) The innodb storage engine supports mvcc row-level locks.

Recommended learning: mysql video tutorial

The above is the detailed content of what is the difference between mysql storage engines. For more information, please follow other related articles on the PHP Chinese website!