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https://dev.mysql.com/doc/refman/8.0/en/timestamp-initialization.html
CREATE TABLE t1 ( ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, dt DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP ); With a DEFAULT clause but no ON UPDATE CURRENT_TIMESTAMP clause, the column has the given ...
https://dev.mysql.com/doc/refman/8.0/en/dynamic-format.html
Dynamic storage format is used if a MyISAM table contains any variable-length columns (VARCHAR, VARBINARY, BLOB, or TEXT), or if the table was created with the ROW_FORMAT=DYNAMIC table option. You can use OPTIMIZE TABLE or myisamchk -r to ...
https://dev.mysql.com/doc/refman/8.0/en/handler.html
] HANDLER tbl_name CLOSE The HANDLER statement provides direct access to table storage engine interfaces. OPEN statement opens a table, making it accessible using subsequent HANDLER ... This table object is not shared by other sessions and is not ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-object-filtering.html
The setup_objects table controls whether the Performance Schema monitors particular table and stored program objects. TABLE filtering affects table I/O events (wait/io/table/sql/handler instrument) and table lock events (wait/lock/table/sql/handler ...The OBJECT_TYPE column indicates the type of object to which a row ...
https://dev.mysql.com/doc/refman/8.0/en/password-management.html
To establish policy for individual accounts, use the PASSWORD EXPIRE option of the CREATE USER and ALTER USER statements. To establish policy for individual accounts, use the PASSWORD HISTORY and PASSWORD REUSE INTERVAL options of the CREATE USER ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-locking.html
Client A creates a table containing two index records (90 and 102) and then starts a transaction that places an exclusive lock on index records with an ID greater than 100. Intention Locks InnoDB supports multiple granularity locking which permits ...Shared and Exclusive Locks Intention Locks Record Locks Gap Locks Next-Key Locks Insert Intention Locks AUTO-INC Locks Predicate Locks for Spatial Indexes Shared and Exclusive Locks InnoDB implements standard row-level locking where there are two types of locks, shared (S) locks and exclusive (X) ...
https://dev.mysql.com/doc/refman/8.0/en/rewriter-query-rewrite-plugin-usage.html
The following example creates a simple rule to match statements that select a single literal value: INSERT INTO query_rewrite.rewrite_rules (pattern, replacement) VALUES('SELECT ?', 'SELECT ? + 1'); The resulting table contents look like this: ...
https://dev.mysql.com/doc/refman/8.0/en/insert.html
For information about generated columns, see Section 15.1.20.8, “CREATE TABLE and Generated Columns”. | TABLE table_name | VALUES row_constructor_list } [ON DUPLICATE KEY UPDATE assignment_list] value: {expr | DEFAULT} value_list: value [, ...
https://dev.mysql.com/doc/refman/8.0/en/external-locking.html
External locking is the use of file system locking to manage contention for MyISAM database tables by multiple processes. External locking is used in situations where a single process such as the MySQL server cannot be assumed to be the only ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-file-defragmenting.html
One symptom of fragmentation is that a table takes more space than it “should” take. Another symptom of fragmentation is that a table scan such as this takes more time than it “should” take: SELECT COUNT(*) FROM t WHERE non_indexed_column <> ... Random insertions into or deletions from a secondary index can cause the index to become ...