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https://dev.mysql.com/doc/refman/8.0/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 ...These rules also apply to existing nonpartitioned tables that you wish to partition using ALTER TABLE ...
https://dev.mysql.com/doc/refman/8.0/en/glossary.html
It saves work for the developer, not to have to produce new unique values when inserting new rows. It provides useful information for the query optimizer, because the column is known to be not null and with unique values. For example, for a column ... These terms are commonly used in information about the MySQL database ...
https://dev.mysql.com/doc/refman/8.0/en/create-index.html
CREATE [UNIQUE | FULLTEXT | SPATIAL] INDEX index_name [index_type] ON tbl_name (key_part,...) [index_option] [algorithm_option | lock_option] ... For a unique index, an error occurs regardless of SQL mode because reducing the index length might ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-ndbd-definition.html
(NDB 8.0.13) A unique node ID is used as the node's address for all cluster internal messages. Unique hash indexes are updated only when the unique index columns are updated, in which case a new entry in the index table is inserted and the old entry ... The [ndbd] and [ndbd default] sections are used to configure the behavior of the cluster's data ...
https://dev.mysql.com/doc/refman/8.0/en/create-table.html
| [CONSTRAINT [symbol]] UNIQUE [INDEX | KEY] [index_name] [index_type] (key_part,...) [index_option] ... IGNORE | REPLACE The IGNORE and REPLACE options indicate how to handle rows that duplicate unique key values when copying a table using a SELECT ...| {FULLTEXT | SPATIAL} [INDEX | KEY] [index_name] (key_part,...) [index_option] ...
https://dev.mysql.com/doc/refman/8.0/en/constraint-primary-key.html
Normally, errors occur for data-change statements (such as INSERT or UPDATE) that would violate primary-key, unique-key, or foreign-key constraints. If you use it, MySQL ignores primary-key or unique-key violations and continues processing with the ...If you are using a transactional storage engine such as InnoDB, MySQL automatically rolls back the ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-locks-set.html
However, only an index record lock is required for statements that lock rows using a unique index to search for a unique row. FOR SHARE statements that use a unique index acquire locks for scanned rows, and release the locks for rows that do not ...
https://dev.mysql.com/doc/refman/8.0/en/miscellaneous-functions.html
There are multiple ways to cause MySQL to accept the query: Alter the table to make name a primary key or a unique NOT NULL column. This enables MySQL to determine that address is functionally dependent on name; that is, address is uniquely ...The ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-limitations-transactions.html
Unique key reads have their locks upgraded automatically by NDB to ensure a self-consistent read; BLOB reads also employ extra locking for consistency. You can help minimize issues with shared read locks by avoiding queries that use unique key ... A ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-options-variables.html
--ndb-deferred-constraints=[0|1] Command-Line Format --ndb-deferred-constraints System Variable ndb_deferred_constraints Scope Global, Session Dynamic Yes SET_VAR Hint Applies No Type Integer Default Value 0 Minimum Value 0 Maximum Value 1 Controls ... This section provides information about MySQL server options, server and status variables that are specific to NDB ...