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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.
The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table.
The FOREIGN KEY constraint in SQL establishes a relationship between two tables by linking columns in one table to those in another. For example, Example: Foreign Key in SQL. Here, the customer_id field in the Orders table is a FOREIGN KEY that references the customer_id field in the Customers table.
22 lip 2024 · This article describes how to create foreign key relationships in SQL Server by using SQL Server Management Studio or Transact-SQL. You create a relationship between two tables when you want to associate rows of one table with rows of another.
To create a new table containing a foreign key column that references another table, use the keyword FOREIGN KEY REFERENCES at the end of the definition of that column. Follow that with the name of the referenced table and the name of the referenced column in parentheses.
A foreign key is a column or a group of columns in one table that uniquely identifies a row of another table (or the same table in case of self-reference). To create a foreign key, you use the FOREIGN KEY constraint.
This tutorial helps you understand SQL foreign key and show you how to define a foreign key using the FOREIGN KEY constraints.
