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https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html
Examples: SELECT SEC_TO_TIME(SUM(TIME_TO_SEC(time_col))) FROM tbl_name; SELECT FROM_DAYS(SUM(TO_DAYS(date_col))) FROM tbl_name; Functions such as SUM() or AVG() that expect a numeric argument cast the argument to a number if necessary. Multiple ...
https://dev.mysql.com/doc/refman/5.7/en/partitioning-columns.html
Columns using other data types relating to dates or times are not supported as partitioning columns. The next two sections discuss COLUMNS partitioning, which are variants on RANGE and LIST partitioning. COLUMNS partitioning enables the use of ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-compression-background.html
Because processors and cache memories have increased in speed more than disk storage devices, many workloads are disk-bound. Data compression enables smaller database size, reduced I/O, and improved throughput, at the small cost of increased CPU ...
https://dev.mysql.com/doc/refman/5.7/en/fulltext-fine-tuning.html
Most full-text variables described in this section must be set at server startup time. Note Minimum and maximum word length full-text parameters do not apply to FULLTEXT indexes created using the ngram parser. The innodb_ft_num_word_optimize option ...You can exert more control over full-text searching behavior if you have a MySQL source distribution because some changes require source code ...
https://dev.mysql.com/doc/refman/5.7/en/view-restrictions.html
The maximum number of tables that can be referenced in the definition of a view is 61. Aliases for column names in CREATE VIEW statements are checked against the maximum column length of 64 characters (not the maximum alias length of 256 ...View ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-memcached-porting-memcached.html
Primary key values are included in secondary indexes, which takes up unnecessary space if the primary key is a long string value. You might create additional secondary indexes on tables that are frequently used to generate reports using SQL. Changes ...This is because InnoDB performs best for large-scale insertions if primary key values are added in sorted order (as they are with auto-increment ...
https://dev.mysql.com/doc/refman/5.7/en/sys-host-summary-by-stages.html
total_latency The total wait time of timed occurrences of the stage event for the host. avg_latency The average wait time per timed occurrence of the stage event for the host. By default, rows are sorted by host and descending total latency. The ...
https://dev.mysql.com/doc/refman/5.7/en/sys-user-summary-by-stages.html
total_latency The total wait time of timed occurrences of the stage event for the user. avg_latency The average wait time per timed occurrence of the stage event for the user. By default, rows are sorted by user and descending total stage latency.
https://dev.mysql.com/doc/refman/5.7/en/internal-locking.html
Deadlocks affect performance rather than representing a serious error, because InnoDB automatically detects deadlock conditions and rolls back one of the affected transactions. At times, it may be more efficient to disable deadlock detection and ...
https://dev.mysql.com/doc/refman/5.7/en/create-index.html
For more information, see Section 13.1.18.8, “Secondary Indexes and Generated Columns”. For a unique index, an error occurs regardless of SQL mode because reducing the index length might enable insertion of nonunique entries that do not meet the ... CREATE [UNIQUE | FULLTEXT | SPATIAL] INDEX index_name [index_type] ON tbl_name (key_part,...) [index_option] [algorithm_option | lock_option] ...