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https://dev.mysql.com/doc/refman/5.7/en/data-size.html
It makes SQL operations faster, by enabling better use of indexes and eliminating overhead for testing whether each value is NULL. If you really need NULL values in your tables, use them. Just avoid the default setting that allows NULL values in ...
https://dev.mysql.com/doc/refman/5.7/en/alter-table-partition-operations.html
Attempting to use REORGANIZE PARTITION without the partition_names INTO (partition_definitions) option on explicitly partitioned tables results in the error REORGANIZE PARTITION without parameters can only be used on auto-partitioned tables using ...
https://dev.mysql.com/doc/refman/5.7/en/charset-unicode-conversion.html
This section describes issues that you may face when converting character data between the utf8mb3 and utf8mb4 character sets. Note This discussion focuses primarily on converting between utf8mb3 and utf8mb4, but similar principles apply to ...
https://dev.mysql.com/doc/refman/5.7/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/5.7/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/5.7/en/group-by-handling.html
The query is invalid if name is not a primary key of t or a unique NOT NULL column. SQL-92 and earlier does not permit queries for which the select list, HAVING condition, or ORDER BY list refer to nonaggregated columns that are not named in the ...
https://dev.mysql.com/doc/refman/5.7/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/5.7/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 8.2.4.1, “Optimizing INSERT ...
https://dev.mysql.com/doc/refman/5.7/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/5.7/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 ...