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https://dev.mysql.com/doc/refman/8.4/en/performance-schema-timing.html
If an enabled instrument is not timed, events produced by the instrument have NULL for the TIMER_START, TIMER_END, and TIMER_WAIT timer values. Events that have not yet completed have an END_EVENT_ID value of NULL. Events are collected by means of ...
https://dev.mysql.com/doc/refman/8.4/en/precision-math-expressions.html
By default, division by zero produces a result of NULL and no warning. sql_mode Value Result '' (Default) No warning, no error; i is set to NULL. With precision math, exact-value numbers are used as given whenever possible. For example, numbers in ...
https://dev.mysql.com/doc/refman/8.4/en/rename-table.html
row *************************** Table: t3 Create Table: CREATE TABLE `t3` ( `i1` int(11) DEFAULT NULL, `i2` int(11) DEFAULT NULL, CONSTRAINT `t3_chk_1` CHECK ((`i1` > 0)), CONSTRAINT `t3_chk_2` CHECK ((`i2` < 0)) ) ENGINE=InnoDB DEFAULT ... RENAME ...
https://dev.mysql.com/doc/refman/8.4/en/show-replica-status.html
In MySQL 8.4, this field is NULL (undefined or unknown) if the replication applier thread is not running, or if the applier thread has consumed all of the relay log and the replication receiver thread is not running. (In older versions of MySQL, ...
https://dev.mysql.com/doc/refman/8.4/en/show-warnings.html
mysql> CREATE TABLE t1 (a TINYINT NOT NULL, b CHAR(4)); Query OK, 0 rows affected (0.05 sec) mysql> INSERT INTO t1 VALUES(10,'mysql'), (NULL,'test'), (300,'xyz'); Query OK, 3 rows affected, 3 warnings (0.00 sec) Records: 3 Duplicates: 0 Warnings: 3 ... SHOW WARNINGS [LIMIT [offset,] row_count] SHOW COUNT(*) WARNINGS SHOW WARNINGS is a diagnostic statement that displays information about the conditions (errors, warnings, and notes) resulting from executing a statement in the current ...
https://dev.mysql.com/doc/refman/8.4/en/spatial-relation-functions-mbr.html
Unless otherwise specified, functions in this section handle their geometry arguments as follows: If any argument is NULL or an empty geometry, the return value is NULL. MBREquals() handles its arguments as described in the introduction to this ...
https://dev.mysql.com/doc/refman/8.4/en/spatial-type-overview.html
MySQL has spatial data types that correspond to OpenGIS classes. The basis for these types is described in Section 13.4.2, “The OpenGIS Geometry Model”. Some spatial data types hold single geometry values: GEOMETRY POINT LINESTRING POLYGON ...
https://dev.mysql.com/doc/refman/8.4/en/static-format.html
NULL columns require additional space in the row to record whether their values are NULL. Each NULL column takes one bit extra, rounded up to the nearest byte. The expected row length in bytes for static-sized rows is calculated using the following ...It is used when the table contains no variable-length columns (VARCHAR, VARBINARY, BLOB, or ...
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-trace-thread.html
Use NULL to collect data for the default of 60 seconds. Dumps all Performance Schema data for an instrumented thread to a .dot formatted graph file (for the DOT graph description language). Each result set returned from the procedure should be used ...
https://dev.mysql.com/doc/refman/8.4/en/using-innodb-tables.html
row *************************** Name: t1 Engine: InnoDB Version: 10 Row_format: Dynamic Rows: 0 Avg_row_length: 0 Data_length: 16384 Max_data_length: 0 Index_length: 0 Data_free: 0 Auto_increment: NULL Create_time: 2021-02-18 12:18:28 Update_time: ... InnoDB tables are created using the CREATE TABLE statement; for example: CREATE TABLE t1 (a INT, b CHAR (20), PRIMARY KEY (a)) ENGINE=InnoDB; The ENGINE=InnoDB clause is not required when InnoDB is defined as the default storage engine, which it is by ...