https://dev.mysql.com/create-tablespace.html
This means that each Disk Data object must be uniquely named (and not merely each Disk Data object of a given type). If the ADD DATAFILE clause is not specified when creating a tablespace, a tablespace data file with a unique file name is created ...
https://dev.mysql.com/data-locks-table.html
If there is no primary key, LOCK_DATA shows either the key values of a selected unique index or the unique InnoDB internal row ID number, according to the rules governing InnoDB clustered index use (see Section 15.6.2.1, “Clustered and Secondary ...For information about which lock requests are blocked by which held locks, see Section 26.12.12.2, “The data_lock_waits ...
https://dev.mysql.com/error-summary-tables.html
The Performance Schema maintains summary tables for aggregating statistical information about server errors (and warnings). For a list of server errors, see Section B.3.1, “Server Error Message Reference”. Collection of error information is ...
https://dev.mysql.com/group-by-handling.html
The query is invalid if name is not a primary key of t or a unique NOT NULL column. SQL-92 and earlier does not permit queries for which the select list, HAVING condition, or ORDER BY list refer to nonaggregated columns that are not named in the ...
https://dev.mysql.com/group-replication-requirements.html
Every table that is to be replicated by the group must have a defined primary key, or primary key equivalent where the equivalent is a non-null unique key. Such keys are required as a unique identifier for every row within a table, enabling the ...
https://dev.mysql.com/innodb-index-types.html
If there is no logical unique and non-null column or set of columns, add a new auto-increment column, whose values are filled in automatically. If you do not define a PRIMARY KEY for your table, MySQL locates the first UNIQUE index where all the key ... Every InnoDB table has a special index called the clustered index where the data for the rows is ...
https://dev.mysql.com/innodb-online-ddl-operations.html
When you create a UNIQUE or PRIMARY KEY index, MySQL must do some extra work. For UNIQUE indexes, MySQL checks that the table contains no duplicate values for the key. If you create a table without a primary key, InnoDB chooses one for you, which ...
https://dev.mysql.com/known-issues.html
If you use ALTER TABLE to add a UNIQUE index to a table used in a MERGE table and then add a normal index on the MERGE table, the key order is different for the tables if there was an old, non-UNIQUE key in the table. This is because ALTER TABLE ...
https://dev.mysql.com/load-data.html
The REPLACE and IGNORE modifiers control handling of input rows that duplicate existing rows on unique key values: If you specify REPLACE, input rows replace existing rows. In other words, rows that have the same value for a primary key or unique ...
https://dev.mysql.com/memory-storage-engine.html
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 issues, or power outages, only use these tables as temporary work areas ...
