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https://dev.mysql.com/doc/refman/5.7/en/insert-on-duplicate.html
If column b is also unique, the INSERT is equivalent to this UPDATE statement instead: UPDATE t1 SET c=c+1 WHERE a=1 OR b=2 LIMIT 1; If a=1 OR b=2 matches several rows, only one row is updated. The ON DUPLICATE KEY UPDATE clause can contain multiple ... If you specify an ON DUPLICATE KEY UPDATE clause and a row to be inserted would cause a duplicate value in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-disk-data-objects.html
It is also possible to specify whether an individual column is stored on disk or in memory by using a STORAGE clause as part of the column's definition in a CREATE TABLE or ALTER TABLE statement. STORAGE DISK causes the column to be stored on disk, ... NDB Cluster Disk Data storage is implemented using a number of Disk Data ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-memory-summary-tables.html
row *************************** EVENT_NAME: memory/sql/TABLE COUNT_ALLOC: 1381 COUNT_FREE: 924 SUM_NUMBER_OF_BYTES_ALLOC: 2059873 SUM_NUMBER_OF_BYTES_FREE: 1407432 LOW_COUNT_USED: 0 CURRENT_COUNT_USED: 457 HIGH_COUNT_USED: 461 ...Operation counts ...
https://dev.mysql.com/doc/refman/5.7/en/compressed-format.html
Compressed storage format is a read-only format that is generated with the myisampack tool. If values in an integer column have a small range, the column is stored using the smallest possible type. For example, a BIGINT column (eight bytes) can be ...Compressed tables have the following characteristics: Compressed tables take very little disk ...
https://dev.mysql.com/doc/refman/5.7/en/constraint-enum.html
ENUM and SET columns provide an efficient way to define columns that can contain only a given set of values. Unless strict mode is disabled (not recommended, but see Section 5.1.10, “Server SQL Modes”), the definition of a ENUM or SET column ...
https://dev.mysql.com/doc/refman/5.7/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. DBAs can use this column to provide information about why a cost estimate row stores a ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-table-reference.html
The following table summarizes all available INFORMATION_SCHEMA tables. For greater detail, see the individual table descriptions. Table 24.1 INFORMATION_SCHEMA Tables Table Name Description Deprecated CHARACTER_SETS Available character sets ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-index-types.html
If a table has no PRIMARY KEY or suitable UNIQUE index, InnoDB generates a hidden clustered index named GEN_CLUST_INDEX on a synthetic column that contains row ID values. If there is no logical unique and non-null column or set of columns to use a ... Each InnoDB table has a special index called the clustered index that stores row ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-timing.html
The columns have these meanings: The TIMER_NAME column shows the names of the available timers. The timers in setup_timers that you can use are those that do not have NULL in the other columns. Processor cycle rate might change, such as when a ...
https://dev.mysql.com/doc/refman/5.7/en/view-restrictions.html
However, a view that is processed with the temptable algorithm is unable to take advantage of indexes on its underlying tables (although indexes can be used during generation of the temporary tables). SHOW CREATE VIEW displays view definitions using ... The maximum number of tables that can be referenced in the definition of a view is ...