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https://dev.mysql.com/doc/refman/8.0/en/user-variables.html
You can store a value in a user-defined variable in one statement and refer to it later in another statement. This enables you to pass values from one statement to another. User variables are written as @var_name, where the variable name var_name ...
https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html
This section describes aggregate functions that operate on sets of values. They are often used with a GROUP BY clause to group values into subsets. If you use an aggregate function in a statement containing no GROUP BY clause, it is equivalent to ...
https://dev.mysql.com/doc/refman/8.0/en/crashing.html
Normally, this is one of the last queries in the log file just before the server restarts. Run the command mysqladmin -i 5 status or mysqladmin -i 5 -r status in a separate window to produce statistics while running other queries. Each MySQL ...
https://dev.mysql.com/doc/refman/8.0/en/derived-tables.html
For information about lateral derived tables preceded by the LATERAL keyword, see Section 15.2.15.9, “Lateral Derived Tables”. A derived table is an expression that generates a table within the scope of a query FROM clause. For example, a ...
https://dev.mysql.com/doc/refman/8.0/en/explain-extended.html
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 EXPLAIN. As of MySQL 8.0.12, extended information is available for SELECT, DELETE, ...
https://dev.mysql.com/doc/refman/8.0/en/information-schema-files-table.html
The FILES table provides information about the files in which MySQL tablespace data is stored. In NDB Cluster, this table also provides information about the files in which NDB Cluster Disk Data tables are stored. For additional information ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-limitations-transactions.html
This issue does not occur for queries that use index or table scans, even against NDB tables having BLOB or TEXT columns. You can help minimize issues with shared read locks by avoiding queries that use unique key lookups that retrieve BLOB or TEXT ... A number of limitations exist in NDB Cluster with regard to the handling of ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-options-variables.html
Two additional sources of information about pushed join performance are available: The status variables Ndb_pushed_queries_defined, Ndb_pushed_queries_dropped, Ndb_pushed_queries_executed, and Ndb_pushed_reads. Setting ndb_row_checksum to 0 means ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-replication-failover.html
In the event that the primary Cluster replication process fails, it is possible to switch over to the secondary replication channel. This means that the ndb_apply_status table contains information for the replica on this host as well as for any ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-indexes.html
Indexes are used to find rows with specific column values quickly. Without an index, MySQL must begin with the first row and then read through the entire table to find the relevant rows. If the table has an index for the columns in question, MySQL ...