FOREIGN KEY. The FOREIGN KEY constraint is a key used to link two tables together. A FOREIGN KEY is a field (or collection of fields) in one table that refers to the PRIMARY KEY in another table.

2025年1月15日 · Foreign keys are a set of constraints in DBMS that establish relationships between tables and also ensure consistency and integrity of data. A foreign key is applied to a column of one table which references the primary key of a column in another table. It act as a cross-reference between two tables.

A foreign key is a set of attributes in a table that refers to the primary key of another table, linking these two tables.

2023年5月4日 · A foreign key is a column or columns in a database that (e.g. table_1.column_a) that are linked to a column in a different table (table_2.column_b). The existence of a foreign key column establishes a foreign key constraint – a database rule that ensures that a value can be added or updated in column_a only if the same value already exists in ...

2020年11月27日 · A SQL foreign key is a field in one table that points to a field in another table (often, the second table's primary key). This links the two database tables, keeping the database consistent and connected.

2025年1月15日 · A FOREIGN KEY constraint is a fundamental concept in relational databases, ensuring data integrity by enforcing relationships between tables. By linking a child table to a parent table, the foreign key establishes referential integrity.

2016年5月24日 · A foreign key is a field that is linked to another table ‘s primary key field in a relationship between two tables. In relational database management systems, a relationship defines a relationship between two or more tables. That is, the data in one table is related to the data in the other.

What is a foreign key? A foreign key is a column or columns of data in one table that refers to the unique data values -- often the primary key data -- in another table. Foreign keys link together two or more tables in a relational database.