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https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-tablestats-table.html
This value might be null if no statistics are collected yet for the table. This value might be null if no statistics are collected yet for the table. The INNODB_TABLESTATS table provides a view of low-level status information about InnoDB tables.
https://dev.mysql.com/doc/refman/8.4/en/information-schema-processlist-table.html
DB The default database for the thread, or NULL if none has been selected. INFO The statement the thread is executing, or NULL if it is executing no statement. Important INFORMATION_SCHEMA.PROCESSLIST is deprecated and subject to removal in a ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-referential-constraints-table.html
The possible values are CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION. The possible values are CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION. The REFERENTIAL_CONSTRAINTS table has these columns: CONSTRAINT_CATALOG The name of the catalog ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-file-defragmenting.html
To speed up index scans, you can periodically perform a “null” ALTER TABLE operation, which causes MySQL to rebuild the table: ALTER TABLE tbl_name ENGINE=INNODB You can also use ALTER TABLE tbl_name FORCE to perform a “null” alter operation ... Random insertions into or deletions from a secondary index can cause the index to become ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-index-types.html
If there is no logical unique and non-null column or set of columns to use a the primary key, add an auto-increment column. If you do not define a PRIMARY KEY for a table, InnoDB uses the first UNIQUE index with all key columns defined as NOT NULL ... Each InnoDB table has a special index called the clustered index that stores row ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-information-schema-files-table.html
FILES columns that are not relevant to InnoDB always return NULL, and are excluded from the query. row *************************** FILE_ID: 0 FILE_NAME: ./ibdata1 FILE_TYPE: TABLESPACE TABLESPACE_NAME: innodb_system FREE_EXTENTS: 0 TOTAL_EXTENTS: 12 ... The Information Schema FILES table provides metadata about all InnoDB tablespace types including file-per-table tablespaces, general tablespaces, the system tablespace, temporary table tablespaces, and undo tablespaces (if ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-redo-log.html
The default value is NULL, which does not permit activating redo log archiving. subdir can be empty, null, or it can be left out. The redo log is a disk-based data structure used during crash recovery to correct data written by incomplete ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-transaction-isolation-levels.html
Transaction isolation is one of the foundations of database processing. Isolation is the I in the acronym ACID; the isolation level is the setting that fine-tunes the balance between performance and reliability, consistency, and reproducibility of ...
https://dev.mysql.com/doc/refman/8.4/en/insert-on-duplicate.html
The VALUES() function is meaningful only as an introducer for INSERT statement value lists, or in the ON DUPLICATE KEY UPDATE clause of an INSERT statement, and returns NULL otherwise. If you specify an ON DUPLICATE KEY UPDATE clause and a row to ...
https://dev.mysql.com/doc/refman/8.4/en/keyring-functions-plugin-specific.html
Return value: Returns 1 for success, or NULL and an error for failure. Return value: Returns 1 for success, or NULL and an error for failure. For each keyring plugin-specific function, this section describes its purpose, calling sequence, and ...