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https://dev.mysql.com/doc/refman/5.7/en/monitor-alter-table-performance-schema.html
stage/innodb/alter table (log apply index): This stage includes the application of DML log generated while ALTER TABLE was running. stage/innodb/alter table (log apply table): This stage includes the application of concurrent DML log generated while ... You can monitor ALTER TABLE progress for InnoDB tables using Performance ...
https://dev.mysql.com/doc/refman/5.7/en/semijoins.html
Assuming that class_num is a primary key in the class table, duplicate suppression is possible by using SELECT DISTINCT, but it is inefficient to generate all matching rows first only to eliminate duplicates later. WHERE ...); Here, ot_i and it_i ...
https://dev.mysql.com/doc/refman/5.7/en/time-zone-support.html
This includes the values displayed by functions such as NOW() or CURTIME(), and values stored in and retrieved from TIMESTAMP columns. Values for TIMESTAMP columns are converted from the session time zone to UTC for storage, and from UTC to the ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-limitations-syntax.html
Keys and indexes on NDB Cluster tables are subject to the following limitations: Column width. Attempting to create an index on an NDB table column whose width is greater than 3072 bytes is rejected with ER_TOO_LONG_KEY: Specified key was too long; ... Some SQL statements relating to certain MySQL features produce errors when used with NDB tables, as described in the following list: Temporary ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-information-schema-temp-table-info.html
The NAME column displays the system-generated name for the temporary table, which is prefixed with “#sql”. The number of columns (N_COLS) is 4 rather than 1 because InnoDB always creates three hidden table columns (DB_ROW_ID, DB_TRX_ID, and ...
https://dev.mysql.com/doc/refman/5.7/en/mathematical-functions.html
With a nonconstant initializer argument (such as a column name), the seed is initialized with the value for each invocation of RAND(). One implication of this behavior is that for equal argument values, RAND(N) returns the same value each time, and ...ABS(X) Returns the absolute value of X, or NULL if X is ...
https://dev.mysql.com/doc/refman/5.7/en/mrr-optimization.html
The MRR optimization is not supported with secondary indexes created on virtual generated columns. When MRR is used, the Extra column in EXPLAIN output shows Using MRR. Reading rows using a range scan on a secondary index can result in many random ...
https://dev.mysql.com/doc/refman/5.7/en/faqs-tablespace-encryption.html
Can indexed columns be encrypted? InnoDB data-at-rest encryption supports all indexes transparently. The master encryption key is generated when tablespace encryption is enabled, and is stored outside the database. The master encryption key is ...Is ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-index-stat.html
The following options are used to generate and update the statistics tables in the NDB kernel. ndb_index_stat provides per-fragment statistical information about indexes on NDB tables. This includes cache version and age, number of index entries ...
https://dev.mysql.com/doc/refman/5.7/en/outer-join-optimization.html
If there is a row in A that matches the WHERE clause, but there is no row in B that matches the ON condition, an extra B row is generated with all columns set to NULL. For a LEFT JOIN, if the WHERE condition is always false for the generated NULL ...