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A foreign key is a set of attributes in a table that refers to the primary key of another table, linking these two tables. In the context of relational databases, a foreign key is subject to an inclusion dependency constraint that the tuples consisting of the foreign key attributes in one relation, R, must also exist in some other (not necessarily distinct) relation, S; furthermore that those ...
Definition: Referential integrity is a database concept that ensures that relationships between tables remain consistent. When one table has a foreign key to another table, the concept of referential integrity states that you may not add a record to the table that contains the foreign key unless there is a corresponding record in the linked table.
Surrogate key. A surrogate key (or synthetic key, pseudokey, entity identifier, factless key, or technical key[citation needed]) in a database is a unique identifier for either an entity in the modeled world or an object in the database. The surrogate key is not derived from application data, unlike a natural (or business) key.
InnoDB is a storage engine for the database management system MySQL and MariaDB. [1] Since the release of MySQL 5.5.5 in 2010, it replaced MyISAM as MySQL's default table type. [2] [3] It provides the standard ACID -compliant transaction features, along with foreign key support ( declarative referential integrity ).
Foreign key refers to a field in a relational table that matches the primary key column of another table. It relates the two keys. Foreign keys need not have unique values in the referencing relation. A foreign key can be used to cross-reference tables, and it effectively uses the values of attributes in the referenced relation to restrict the ...
MySQL ( / ˌmaɪˌɛsˌkjuːˈɛl /) [5] is an open-source relational database management system (RDBMS). [5] [6] Its name is a combination of "My", the name of co-founder Michael Widenius 's daughter My, [7] and "SQL", the acronym for Structured Query Language.
A non-primary key that can be used to identify only one row in a table. Alternate keys may be used like a primary key in a single-table select. Foreign. A key that has migrated to another entity. At the most basic definition, "a key is a unique identifier", [1] so unique key is a pleonasm.
MySQL Federated – allows a user to create a table that is a local representation of a foreign (remote) table. It utilizes the MySQL client library API as a data transport, treating the remote data source the same way other storage engines treat local data sources whether they be MYD files (MyISAM), memory (Cluster, Heap), or tablespace (InnoDB).