Rechercher dans le manuel MySQL
Search Results
https://dev.mysql.com/mysql-cluster-ndbinfo-operations-per-fragment.html
This currently has the following formats: Base table: - DbName/def/TblName BLOB table: - DbName/def/NDB$BLOB_BaseTblId_ColNo Ordered index: - sys/def/BaseTblId/IndexName Unique index: - sys/def/BaseTblId/IndexName$unique The $unique suffix shown for ... The operations_per_fragment table provides information about the operations performed on individual fragments and fragment replicas, as well as about some of the results from these ...
https://dev.mysql.com/mysql-cluster-options-variables.html
Controls whether or not constraint checks on unique indexes are deferred until commit time, where such checks are supported. This includes all rows read by any primary key, unique key, or scan operation made in this client session. This includes all ... This section provides information about MySQL server options, server and status variables that are specific to NDB ...
https://dev.mysql.com/merge-table-problems.html
A MERGE table cannot maintain uniqueness constraints over the entire table. MySQL ensures that unique key values remain unique within that MyISAM table, but not over all the underlying tables in the collection. Because the MERGE engine cannot ...
https://dev.mysql.com/group-by-functional-dependence.html
The examples use this notation: {X} -> {Y} Understand this as “X uniquely determines Y,” which also means that Y is functionally dependent on X. A UNIQUE index over a NOT NULL column could be used instead of a primary key and the same functional ... The following discussion provides several examples of the ways in which MySQL detects functional ...
https://dev.mysql.com/mysql-cluster-log-statistics.html
This count also includes reads performed as part of unique index operations. A unique index read operation generates 2 primary key read operations—1 for the hidden unique index table, and 1 for the table on which the read takes place. This ... The ...
https://dev.mysql.com/mysql-cluster-replication-issues.html
In older versions of NDB Cluster, operations that updated values of unique key columns of NDB tables could result in duplicate-key errors when replicated. This issue is solved for replication between NDB tables by deferring unique key checks until ... This section discusses known problems or issues when using replication with NDB Cluster ...
https://dev.mysql.com/columns-table.html
COLUMN_KEY Whether the column is indexed: If COLUMN_KEY is empty, the column either is not indexed or is indexed only as a secondary column in a multiple-column, nonunique index. If COLUMN_KEY is UNI, the column is the first column of a UNIQUE index. (A UNIQUE index permits multiple NULL values, but you can tell whether the column permits NULL by checking the Null column.) If COLUMN_KEY is MUL, the column is the first column of a nonunique index in which multiple occurrences of a given value are permitted within the ...
https://dev.mysql.com/explain-output.html
const is used when you compare all parts of a PRIMARY KEY or UNIQUE index to constant values. It is used when all parts of an index are used by the join and the index is a PRIMARY KEY or UNIQUE NOT NULL index. ref is used if the join uses only a ...
https://dev.mysql.com/keyring-service.html
A “record” in the keystore consists of data (the key itself) and a unique identifier through which the key is accessed. The key_id and user_id arguments form a unique combination indicating which key in the keyring to use. Syntax: bool ... MySQL ...
https://dev.mysql.com/mysql-cluster-programs-ndb-desc.html
ndb_desc provides a detailed description of one or more NDB tables. Usage ndb_desc -c connection_string tbl_name -d db_name [options] ndb_desc -c connection_string index_name -d db_name -t tbl_name Additional options that can be used with ndb_desc ...
Document created the 26/06/2006, last modified the 26/10/2018
Source of the printed document:https://www.gaudry.be/en/mysql-rf-fct-unique-p-2.html
The infobrol is a personal site whose content is my sole responsibility. The text is available under CreativeCommons license (BY-NC-SA). More info on the terms of use and the author.
References
These references and links indicate documents consulted during the writing of this page, or which may provide additional information, but the authors of these sources can not be held responsible for the content of this page.
The author This site is solely responsible for the way in which the various concepts, and the freedoms that are taken with the reference works, are presented here. Remember that you must cross multiple source information to reduce the risk of errors.
