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https://dev.mysql.com/doc/refman/8.0/en/switchable-optimizations.html
In MySQL 8.0.18 and later, this also controls use of hash joins, as do the BNL and NO_BNL optimizer hints. In MySQL 8.0.20 and later, block nested loop support is removed from the MySQL server, and this flag controls the use of hash joins only, as ...Its value is a set of flags, each of which has a value of on or off to indicate whether the corresponding optimizer behavior is enabled or ...
https://dev.mysql.com/doc/refman/8.0/en/trigger-syntax.html
The trigger acts as an accumulator, summing the values inserted into one of the columns of the table. In this case, the trigger activates before each row inserted into the table. In the example, the trigger body is a simple SET that accumulates into ... To create a trigger or drop a trigger, use the CREATE TRIGGER or DROP TRIGGER statement, described in Section 15.1.22, “CREATE TRIGGER Statement”, and Section 15.1.34, “DROP TRIGGER ...
https://dev.mysql.com/doc/refman/8.0/en/create-tablespace.html
The UNDO keyword, introduced in MySQL 8.0.14, must be specified to create an undo tablespace. The unique file name is a 128 bit UUID formatted into five groups of hexadecimal numbers separated by dashes (aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee). The ...
https://dev.mysql.com/doc/refman/8.0/en/derived-tables.html
For information about lateral derived tables preceded by the LATERAL keyword, see Section 15.2.15.9, “Lateral Derived Tables”. A derived table is an expression that generates a table within the scope of a query FROM clause. For example, a ...
https://dev.mysql.com/doc/refman/8.0/en/example-foreign-keys.html
MySQL supports foreign keys, which permit cross-referencing related data across tables, and foreign key constraints, which help keep the related data consistent. This following example relates parent and child tables through a single-column foreign ...A foreign key relationship involves a parent table that holds the initial column values, and a child table with column values that reference the parent column ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-compression-syntax-warnings.html
The “non-strict” behavior lets you import a mysqldump file into a database that does not support compressed tables, even if the source database contained compressed tables. To import the dump file into a new database, and have the tables ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-information-schema-system-tables.html
The InnoDB INFORMATION_SCHEMA table interface allows you to query this data using SQL. As a final step, insert a row into table t1 (TABLE_ID = 71) and view the data in the INNODB_TABLESTATS table. mysql> INSERT INTO t1 VALUES(5, 'abc', 'def'); Query ... You can extract metadata about schema objects managed by InnoDB using InnoDB INFORMATION_SCHEMA ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-transaction-isolation-levels.html
For other search conditions, InnoDB locks the index range scanned, using gap locks or next-key locks to block insertions by other sessions into the gaps covered by the range. Gap locking is only used for foreign-key constraint checking and ...
https://dev.mysql.com/doc/refman/8.0/en/invisible-indexes.html
If an index made invisible actually is needed or used by the optimizer, there are several ways to notice the effect of its absence on queries for the table: Errors occur for queries that include index hints that refer to the invisible index. If the ... MySQL supports invisible indexes; that is, indexes that are not used by the ...
https://dev.mysql.com/doc/refman/8.0/en/locking-service.html
MySQL distributions provide a locking interface that is accessible at two levels: At the SQL level, as a set of loadable functions that each map onto calls to the service routines. As a C language interface, callable as a plugin service from server ...For general information about plugin services, see Section 7.6.9, “MySQL Plugin ...