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https://dev.mysql.com/doc/refman/9.7/en/cost-model.html
To generate execution plans, the optimizer uses a cost model that is based on estimates of the cost of various operations that occur during query execution. The optimizer has a set of compiled-in default “cost constants” available to it to make ...
https://dev.mysql.com/doc/refman/9.7/en/create-table-generated-columns.html
Values of a generated column are computed from an expression included in the column definition. Generated column definitions have this syntax: col_name data_type [GENERATED ALWAYS] AS (expr) [VIRTUAL | STORED] [NOT NULL | NULL] [UNIQUE [KEY]] ...
https://dev.mysql.com/doc/refman/9.7/en/example-auto-increment.html
You can also explicitly assign 0 to the column to generate sequence numbers, unless the NO_AUTO_VALUE_ON_ZERO SQL mode is enabled. For example: INSERT INTO animals (id,name) VALUES(0,'groundhog'); If the column is declared NOT NULL, it is also ...
https://dev.mysql.com/doc/refman/9.7/en/information-schema-innodb-trx-table.html
The INNODB_TRX table provides information about every transaction currently executing inside InnoDB, including whether the transaction is waiting for a lock, when the transaction started, and the SQL statement the transaction is executing, if any.
https://dev.mysql.com/doc/refman/9.7/en/information-schema-partitions-table.html
Each row in this table corresponds to an individual partition or subpartition of a partitioned table. The PARTITIONS table has these columns: TABLE_CATALOG The name of the catalog to which the table belongs. TABLE_SCHEMA The name of the schema ...
https://dev.mysql.com/doc/refman/9.7/en/invisible-columns.html
An invisible column is normally hidden to queries, but can be accessed if explicitly referenced. As an illustration of when invisible columns may be useful, suppose that an application uses SELECT * queries to access a table, and must continue to ...
https://dev.mysql.com/doc/refman/9.7/en/performance-schema-events-transactions-current-table.html
The table stores one row per thread showing the current status of the thread's most recent monitored transaction event, so there is no system variable for configuring the table size. For example: mysql> SELECT * FROM ...
https://dev.mysql.com/doc/refman/9.7/en/rewriter-query-rewrite-plugin-usage.html
To enable or disable the plugin, enable or disable the rewriter_enabled system variable. By default, the Rewriter plugin is enabled when you install it (see Section 7.6.4.1, “Installing or Uninstalling the Rewriter Query Rewrite Plugin”). To ...
https://dev.mysql.com/doc/refman/9.7/en/selecting-all.html
For example, you may happen to think that the birth date for Bowser doesn't seem quite right. Consulting your original pedigree papers, you find that the correct birth year should be 1989, not 1979. Fix only the erroneous record with an UPDATE ...
https://dev.mysql.com/doc/refman/9.7/en/selecting-rows.html
As shown in the preceding section, it is easy to retrieve an entire table. But typically you don't want to see the entire table, particularly when it becomes large. Instead, you're usually more interested in answering a particular question, in ...