https://dev.mysql.com/char.html
The length of a CHAR column is fixed to the length that you declare when you create the table. In contrast to CHAR, VARCHAR values are stored as a 1-byte or 2-byte length prefix plus data. The length prefix indicates the number of bytes in the value. InnoDB encodes fixed-length fields greater than or equal to 768 bytes in length as variable-length fields, which can be stored ...
https://dev.mysql.com/charset-configuration.html
In such cases, starting the mysql client with --default-character-set=system_character_set—that is, setting the client character set to match the system character set—should fix the problem. The MySQL server has a compiled-in default character ...
https://dev.mysql.com/custom-benchmarks.html
After fixing one bottleneck (or by replacing it with a “dummy” module), you can proceed to identify the next bottleneck. Most of the time, these problems would be much easier to fix if the systems were not already in production. Benchmark your ...
https://dev.mysql.com/data-types.html
For floating-point and fixed-point types, M is the total number of digits that can be stored (the precision). D applies to floating-point and fixed-point types and indicates the number of digits following the decimal point (the scale). MySQL ...
https://dev.mysql.com/dynamic-format.html
If you have fixed-length columns that you access or change frequently in a table that also contains some variable-length columns, it might be a good idea to move the variable-length columns to other tables just to avoid fragmentation. Much less disk ... Dynamic storage format is used if a MyISAM table contains any variable-length columns (VARCHAR, VARBINARY, BLOB, or TEXT), or if the table was created with the ROW_FORMAT=DYNAMIC table ...
https://dev.mysql.com/group-replication-frequently-asked-questions.html
You need to find out why a member is lagging behind and fix that or remove the member from the group. Alternatively, another way of fixing the issue specifically in Group Replication is to issue a STOP GROUP_REPLICATION statement and then a START ...
https://dev.mysql.com/innodb-system-tablespace.html
If the previous last data file is defined with the keyword autoextend, change its definition to use a fixed size, based on how large it has actually grown. The InnoDB system tablespace is the storage area for the doublewrite buffer and the change ...
https://dev.mysql.com/internal-temporary-tables.html
When in-memory internal temporary tables are managed by the MEMORY storage engine, fixed-length row format is used. Columns take only as much storage as needed, which reduces disk I/O, space requirements, and processing time compared to on-disk ...
https://dev.mysql.com/memory-storage-engine.html
Variable-length types such as VARCHAR are stored using a fixed length. The MEMORY storage engine (formerly known as HEAP) creates special-purpose tables with contents that are stored in memory. Because the data is vulnerable to crashes, hardware ...
https://dev.mysql.com/myisam-table-formats.html
Two of them, fixed and dynamic format, are chosen automatically depending on the type of columns you are using. When you use CREATE TABLE or ALTER TABLE for a table that has no BLOB or TEXT columns, you can force the table format to FIXED or DYNAMIC ...The third, compressed format, can be created only with the myisampack utility (see Section 4.6.6, “myisampack — Generate Compressed, Read-Only MyISAM ...