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https://dev.mysql.com/doc/refman/8.4/en/information-schema-tables-table.html
Not all storage engines update this time, in which case, the value is always NULL. For views, most TABLES columns are 0 or NULL except that TABLE_NAME indicates the view name, CREATE_TIME indicates the creation time, and TABLE_COMMENT says VIEW. The ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-fulltext-index.html
If you want to create your own FTS_DOC_ID column, the column must be defined as BIGINT UNSIGNED NOT NULL and named FTS_DOC_ID (all uppercase), as in the following example: Note The FTS_DOC_ID column does not need to be defined as an AUTO_INCREMENT ... Full-text indexes are created on text-based columns (CHAR, VARCHAR, or TEXT columns) to speed up queries and DML operations on data contained within those ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-optimize-tablespace-page-allocation.html
By default, when additional space is required, InnoDB allocates pages to the tablespace and physically writes NULLs to those pages. You can disable innodb_extend_and_initialize on Linux systems to avoid physically writing NULLs to newly allocated ...
https://dev.mysql.com/doc/refman/8.4/en/merge-storage-engine.html
The column of the underlying table and the MERGE table can be NULL. The MERGE storage engine, also known as the MRG_MyISAM engine, is a collection of identical MyISAM tables that can be used as one. “Identical” means that all tables have ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-dict-obj-tree.html
The dict_obj_tree table provides a tree-based view of table information from the dict_obj_info table. This is intended primarily for use in testing, but can be useful in visualizing hierarchies of NDB database objects. This means that you must know ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-programs-ndb-restore.html
The following changes in primary key definitions are supported by --allow-pk-changes: Extending the primary key: A non-nullable column that exists in the table schema in the backup becomes part of the table's primary key in the database. This option ... The NDB Cluster restoration program is implemented as a separate command-line utility ndb_restore, which can normally be found in the MySQL bin ...
https://dev.mysql.com/doc/refman/8.4/en/non-typed-operators.html
->> Return value from JSON column after evaluating path and unquoting the result; equivalent to JSON_UNQUOTE(JSON_EXTRACT()). / Division operator := Assign a value = Assign a value (as part of a SET statement, or as part of the SET clause in an ...
https://dev.mysql.com/doc/refman/8.4/en/optimizer-hints.html
row *************************** id: 1 select_type: SIMPLE table: t1 partitions: NULL type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 256 filtered: 100.00 Extra: Using filesort The USE INDEX, FORCE INDEX, and IGNORE INDEX index ... One means of control over optimizer strategies is to set the optimizer_switch system variable (see Section 10.9.2, “Switchable ...
https://dev.mysql.com/doc/refman/8.4/en/other-vendor-data-types.html
To facilitate the use of code written for SQL implementations from other vendors, MySQL maps data types as shown in the following table. These mappings make it easier to import table definitions from other database systems into MySQL. If you create ...
https://dev.mysql.com/doc/refman/8.4/en/outer-join-optimization.html
If there is a row in A that matches the WHERE clause, but there is no row in B that matches the ON condition, an extra B row is generated with all columns set to NULL. For a LEFT JOIN, if the WHERE condition is always false for the generated NULL ...