Sustainability of Digital Formats: Planning for Library of Congress Collections

The MySQL Table Definition Format (FRM) is an internal systems file which stores the metadata used to form table definition (column names and other relationship metadata) of a MySQL or MariaDB database. MySQL and MariaDB are both relational database management systems (RDBMS). An FRM file is always used in tandem with either a MySQL Database Data File (MYI) or MyISAM Indexes File (MYD) file, which store the contents of the database. Earlier versions of MySQL and MariaDB would automatically create an FRM file based on the table names. There is no restriction to how many tables a database can hold.

Both MySQL and MariaDB have removed FRM files from their current versions. MySQL deprecated FRM in version 8.0 and MariaDB deprecated it in version 11.0. The file type was not replaced with a different file type. Instead, both MySQL and MariaDB retain the data previously saved in an FRM file directly within the software.

FRM in the filename extension is short for "FoRM." This is a legacy terminology from a predecessor to MySQL called UNIREG (ca. 1979), which used the term "form" instead of "table" to represent database structure.

MySQL was created by MySQL AB, a Swedish company founded by David Axmark, Allan Larsson and Michael "Monty" Widenius. It was named after Widenius’ daughter My. MySQL is a proprietary software owned by Oracle. Widenius left MySQL in 2010 and created a new RDBMS named MariaDB (named for his second daughter Maria). MariaDB utilizes the same file types as MySQL, operates on the same logic, and is open source. Generally, statements about the MySQL Table Definition Format may be applied to both MySQL and MariaDB systems.

MySQL versions 5.7 and earlier automatically generated table-based FRM files whenever a new table was created. These files will always be in binary.

MySQL users can prompt a 'CREATE VIEW' database action, which will create a plain text file with the FRM extension. These files are not the same as the MySQL Table Definition Format. See MySQL View Definition Format for more information.

MySQL has the option to use different storage engines (e.g. MyISAM or InnoDB), but FRM files are generated regardless of the chosen storage engine. See "Relationship to other formats" for more details about additional files that are stored alongside FRM files as they differ based on the chosen storage engine.

As a deprecated method of recordkeeping during production, documentation is limited and only available in legacy materials. MySQL has removed some of this information from its legacy documentation.

Official documentation "MySQL .frm File Format" (link via Internet Archive).

This file, although now deprecated, is part of the widely used MySQL and MariaDB RDBMS. MySQL is the second-most popular database in the world according to DB-Engines with MariaDB ranking as #12. Many large organizations use MySQL, including Facebook, Twitter, Booking.com, and Verizon.

Dozens of programming languages integrate with MySQL, including Ada, C, C#, C++, D, Delphi, Eiffel, Erlang, Haskell, Java, JavaScript, (Node.js), Objective-C, OCaml, Perl, PHP, Python, Ruby, Scheme, and Tcl.

None associated with the basic format. No license is required in creating, modifying, or exporting FRM files.

A matching version of MySQL must be used to load and transform FRM files.

This file is itself self-documentation for the MySQL database format. The MySQL Table Definition Format file preserves the table and the relationship between data within the database, but none of the data itself.

The file stores the version it was created in. The version history can be retrieved using MySQL tooling or by checking the value of binary hex offset 0x33.

MySQL version 5.7 or earlier and a matching version of the software that created the file.

None. There is no built-in mechanism for encryption, compression, or intellectual property protection.

MySQL Table Definition Format files are used in MySQL 5.7 and earlier databases during production. This file stores information about a table and one is created for each table in the database. There can be many FRM files in each database as there is no limitation for the number of tables per database.

This file is limited to MySQL versions 5.7 and earlier. Editing can be done using the MySQL system via command line, desktop-based software such as MySQL Workbench, or web-based technology such as phpMyAdmin.

MySQL Table Definition files are stored in MySQL's data directory. This location will vary depending on the installation and machine. By default, the data directory can be found at the path /usr/local/mysql/for Linux and Mac machines.For Windows, that default path is C:\Program Files\MySQL.

A MySQL database can be restored from backup with an FRM file and its matching .MYI and .MYD files (for databases using the MyISAM storage engine) or .IBD file (for the InnoDB storage engine).

MySQL was created in 1995 by Swedish company MySQL AB which was founded by David Axmark, Allan Larsson and Michael "Monty" Widenius. The first internal release of MySQL was on May 23, 1995. MySQL is named after co-founder Monty Widenius's daughter, My.

In 2008, the company was sold to Sun Microsystems. In 2010, Sun Microsystems was purchased by Oracle. Co-founder Widenius opposed the Oracle acquisition and left to found his own RDBMS, MariaDB, based upon MySQL's open source codebase. Just as MySQL is named for Widenius' eldest daughter My, MariaDB is named for his second daughter Maria. This familiar relationship between MySQL and MariaDB is why both RDBMS are remarkably similar and both utilize the FRM format.