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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 following SQL creates a FOREIGN KEY on the "PersonID" column when the "Orders" table is created:
ALTER TABLE child_table_name ADD FOREIGN KEY (child_table_column) REFERENCES parent_table_name(parent_table_column); child_table_name is that table in which we want to add constraint. child_table_column is that table column in which we want to add foreign key.
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.
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.
Adding FOREIGN KEY contraints to existing tables. To add a FOREIGN KEY constraint to existing table, you use the ALTER TABLE statement. ALTER TABLE table_1 ADD CONSTRAINT fk_name FOREIGN KEY (fk_key_column) REFERENCES table_2(pk_key_column) Code language: SQL (Structured Query Language) (sql)
25 maj 2018 · This article demonstrates how to create a foreign key constraint in SQL Server, using Transact-SQL. Example. The easiest way to demonstrate this is with an example. In this example, we use T-SQL to create a foreign key constraint using the ALTER TABLE statement:
