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https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-cluster-locks.html
If a transaction holds an exclusive lock on a given row, all other locks on that row have the same transaction ID. When the detail column contains a * (asterisk character), this means that this lock is the first holding lock in the affected row's ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-server-locks.html
If a transaction has an exclusive lock on a given row, all other locks on that row have the same transaction ID. The detail column indicates whether this lock is the first holding lock in the affected row's lock queue, in which case it contains a * ... The server_locks table is similar in structure to the cluster_locks table, and provides a subset of the information found in the latter table, but which is specific to the SQL node (MySQL server) where it ...
https://dev.mysql.com/doc/refman/8.4/en/mysqlimport.html
--replace, -r Command-Line Format --replace The --replace and --ignore options control handling of input rows that duplicate existing rows on unique key values. If you specify --replace, new rows replace existing rows that have the same unique key ... The mysqlimport client provides a command-line interface to the LOAD DATA SQL ...
https://dev.mysql.com/doc/refman/8.4/en/optimizer-hints.html
Consider this statement: SELECT /*+ BNL(t2) */ FROM t1, t2; If the optimizer chooses to process t1 first, it applies a Block Nested-Loop join to t2 by buffering the rows from t1 before starting to read from t2. ORDER_INDEX, NO_ORDER_INDEX: Cause ...
https://dev.mysql.com/doc/refman/8.4/en/outer-join-optimization.html
The LEFT JOIN condition is used to decide how to retrieve rows from table B. 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 ...MySQL implements an A LEFT JOIN B join_specification as follows: Table B is set to depend on table A and all tables on which A ...
https://dev.mysql.com/doc/refman/8.4/en/partitioning-limitations-partitioning-keys-unique-keys.html
This section discusses the relationship of partitioning keys with primary keys and unique keys. The rule governing this relationship can be expressed as follows: All columns used in the partitioning expression for a partitioned table must be part ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-atom-molecule-events.html
For a table I/O event, there are usually two rows in events_waits_current, not one. For example, a row fetch might result in rows like this: Row# EVENT_NAME TIMER_START TIMER_END ---- ---------- ----------- --------- 1 wait/io/file/myisam/dfile ...
https://dev.mysql.com/doc/refman/8.4/en/replication-rules-examples.html
It is also important to note that the results vary depending on whether the operation is logged using statement-based or row-based binary logging format. With row-based format, DML statements are handled based on the database where the modified ...
https://dev.mysql.com/doc/refman/8.4/en/set.html
Normally, you search for SET values using the FIND_IN_SET() function or the LIKE operator: mysql> SELECT * FROM tbl_name WHERE FIND_IN_SET('value',set_col)>0; mysql> SELECT * FROM tbl_name WHERE set_col LIKE '%value%'; The first statement finds rows ... A SET is a string object that can have zero or more values, each of which must be chosen from a list of permitted values specified when the table is ...
https://dev.mysql.com/doc/refman/8.4/en/subquery-errors.html
Incorrect number of rows from subquery: ERROR 1242 (ER_SUBSELECT_NO_1_ROW) SQLSTATE = 21000 Message = "Subquery returns more than 1 row" This error occurs for statements where the subquery must return at most one row but returns multiple rows. All ...