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What is myisam in mysql? In view of this problem, this article introduces the corresponding analysis and answers in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible way.

Myisam introduction

MyISAM is the default storage engine (before Mysql5.1). It is based on older ISAM code, but has many useful extensions. (note that ISAM is not supported in MySQL 5.1). Each MyISAM is stored as three files on disk, and the name of each file starts with the name of the table, and the extension indicates the file type.

.frm file storage table definition

The MYD (MYData) file stores data from the table

The .MYI (MYIndex) file stores the index of the table.

Detailed introduction

To make it clear that you want to use a MyISAM table, use the ENGINE option to indicate:

CREATE TABLE t (I INT) ENGINE = MYISAM

Note: older versions of MySQL used TYPE instead of ENGINE (for example, TYPE = MYISAM). MySQL 5.1 supports this syntax for backward compatibility, but TYPE is now despised, and ENGINE is the first usage.

In general, the ENGINE option is unnecessary; unless the default has been changed, InnoDB is the default storage engine (after Mysql 5.1).

Some features of MyISAM storage engine

1. All data values are stored in low bytes first.

This separates the modem from the operating system. The only requirement for binary portability is that machines use complements (as they have in the last 20 years) and IEEE floating-point formats (which are also completely dominant in mainstream machines). The only machine that does not support binary compatibility is the embedded system. These systems sometimes use special processors.

Storing low bytes of data first does not seriously affect speed; bytes in data rows are generally unjoined, and reading unjoined bytes in one direction does not take more resources than reading them in reverse. The code on the server that gets the column value does not seem to be running out of time compared to other code.

2. Large files (up to 63-bit file length) are supported on file systems and operating systems that support large files.

3. When deleting and updating and inserting are mixed, dynamic-sized rows are less fragmented. This is done automatically by merging adjacent deleted blocks and extending to the next block if the next block is deleted.

This is the answer to the question about what myisam is in mysql. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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