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https://dev.mysql.com/doc/refman/8.4/en/counting-rows.html
Counting the total number of animals you have is the same question as “How many rows are in the pet table?” because there is one record per pet. COUNT(*) counts the number of rows, so the query to count your animals looks like this: mysql> ...
https://dev.mysql.com/doc/refman/8.4/en/create-table-check-constraints.html
expr specifies the constraint condition as a boolean expression that must evaluate to TRUE or UNKNOWN (for NULL values) for each row of the table. CREATE TABLE permits the core features of table and column CHECK constraints, for all storage engines. CREATE TABLE permits the following CHECK constraint syntax, for both table constraints and column constraints: [CONSTRAINT [symbol]] CHECK (expr) [[NOT] ENFORCED] The optional symbol specifies a name for the ...
https://dev.mysql.com/doc/refman/8.4/en/events-configuration.html
row *************************** Id: 1 User: root Host: localhost db: NULL Command: Query Time: 0 State: NULL Info: show processlist *************************** 2. row *************************** Id: 2 User: event_scheduler Host: localhost db: NULL ... Events are executed by a special event scheduler thread; when we refer to the Event Scheduler, we actually refer to this ...
https://dev.mysql.com/doc/refman/8.4/en/gis-wkb-functions.html
Unless otherwise specified, functions in this section handle their geometry arguments as follows: If the WKB or SRID argument is NULL, the return value is NULL. If the options argument is NULL, the return value is NULL. These functions take as ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-troubleshooting-datadict.html
A warning is issued indicating that InnoDB is attempting to import the file without schema verification. Information about table definitions is stored in the InnoDB data dictionary. If you move data files around, dictionary data can become ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-operations-per-fragment.html
The operations_per_fragment table provides information about the operations performed on individual fragments and fragment replicas, as well as about some of the results from these operations. This currently has the following formats: Base table: ...
https://dev.mysql.com/doc/refman/8.4/en/optimizing-innodb-bulk-data-loading.html
For optimal performance when loading data into an InnoDB FULLTEXT index, follow this set of steps: Define a column FTS_DOC_ID at table creation time, of type BIGINT UNSIGNED NOT NULL, with a unique index named FTS_DOC_ID_INDEX. For example: CREATE ... These performance tips supplement the general guidelines for fast inserts in Section 10.2.5.1, “Optimizing INSERT ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-firewall-groups-table.html
The value is NULL, or a non-NULL account that has the format user_name@host_name: If the value is NULL, the firewall records allowlist rules for statements received from any account that is a member of the group. If the value is non-NULL, the ...
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 ...