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https://dev.mysql.com/doc/refman/5.7/en/stored-programs-logging.html
If this is not the case, an error is generated and the function does not run, unless log_bin_trust_function_creators=1 is specified to override this check (see below). SELECT statements when the source column expressions refer to local variables.
https://dev.mysql.com/doc/refman/5.7/en/derived-tables.html
A derived table is an expression that generates a table within the scope of a query FROM clause. This does not work: SELECT AVG(SUM(column1)) FROM t1 GROUP BY column1; However, this query provides the desired information: SELECT AVG(sum_column1) ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-innodb-table-reference.html
The following table summarizes INFORMATION_SCHEMA InnoDB tables. For greater detail, see the individual table descriptions. Table 24.3 INFORMATION_SCHEMA InnoDB Tables Table Name Description Deprecated INNODB_BUFFER_PAGE Pages in InnoDB buffer pool ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-multi-versioning.html
If InnoDB generates a clustered index automatically, the index contains row ID values. Records in a clustered index are updated in-place, and their hidden system columns point undo log entries from which earlier versions of records can be ...It ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo-locks-per-fragment.html
The values shown in all of the columns ex_req, ex_req_imm_ok, ex_wait_ok, ex_wait_fail, sh_req, sh_req_imm_ok, sh_wait_ok, and sh_wait_fail represent cumulative numbers of requests since the table or fragment was created, or since the last restart ... The locks_per_fragment table provides information about counts of lock claim requests, and the outcomes of these requests on a per-fragment basis, serving as a companion table to operations_per_fragment and ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-socket-instances-table.html
The socket_instances table has these columns: EVENT_NAME The name of the wait/io/socket/* instrument that produced the event. Instead, an event is generated in the events_waits_current table with an EVENT_NAME value of idle. This combination value ... The socket_instances table provides a real-time snapshot of the active connections to the MySQL ...
https://dev.mysql.com/doc/refman/5.7/en/precision-math-rounding.html
This section discusses precision math rounding for the ROUND() function and for inserts into columns with exact-value types (DECIMAL and integer). The ROUND() function rounds differently depending on whether its argument is exact or approximate: ...
https://dev.mysql.com/doc/refman/5.7/en/problems-connecting.html
Check this by executing mysql -u root mysql and issuing this SQL statement: SELECT * FROM user; The result should include a row with the Host and User columns matching your client's host name and your MySQL user name. If you do not know the IP ...
https://dev.mysql.com/doc/refman/5.7/en/explain-extended.html
The Message value in SHOW WARNINGS output displays how the optimizer qualifies table and column names in the SELECT statement, what the SELECT looks like after the application of rewriting and optimization rules, and possibly other notes about the ... For SELECT statements, the EXPLAIN statement produces extra (“extended”) information that is not part of EXPLAIN output but can be viewed by issuing a SHOW WARNINGS statement following ...
https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-optimization-tips.html
Similarly, if your application computes a single result based on several column values or large volumes of data, combining the computation into a loadable function can help performance. If possible, classify reports as “live” or as ... This ...