![]() ![]() Using SQL Server Management Studio To modify a foreign key The new foreign key column must match the data type and size of the primary key column to which it relates, with these exceptions:Ī char column or sysname column can relate to a varchar column.Ī binary column can relate to a varbinary column.Īn alias data type can relate to its base type. Modifying a table's foreign key changes which columns are related to columns in the primary key table.īefore You Begin Limitations and Restrictions You can modify the foreign key side of a relationship in SQL Server by using SQL Server Management Studio or Transact-SQL. Got a question for us? Please mention it in the comments section of this article on “Foreign Key SQL” and I will get back to you.SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance This training will help you understand MySQL in-depth and help you achieve mastery over the subject. If you wish to learn more about MySQL and get to know this open-source relational database, then check out our MySQL DBA Certification Training which comes with instructor-led live training and real-life project experience. I hope you understood how to use Foreign Key in SQL. With this, we come to an end to this article. To drop the foreign key, you can refer to the following example: ![]() Next, in this article on Foreign Key SQL, let us understand how to drop a foreign key Drop Foreign Key If you wish to add a name to the Foreign Key constraint and define it on multiple columns, use the following SQL syntax:įOREIGN KEY (customerID) REFERENCES Customers(customerID) You can use the following syntax to create a foreign key on the “customerID” column when the “courses” table is already created and you just want to alter the table:ĪDD FOREIGN KEY (customerID) REFERENCES customers(customerID) Next, in this article on Foreign Key SQL, let us see how to use the foreign key on Alter Table.įor a detailed, You can even check out the details of relational databases, functions, queries, variables, etc with the SQL Course. To apply foreign key on multiple columns while creating a table, refer to the following example:ĬONSTRAINT FK_CustomerCourse FOREIGN KEY (customerID) You can use the following syntax to create a foreign key on the “customerID” column when you create “courses” table:ĬustomerID int FOREIGN KEY REFERENCES customers(customerID)įOREIGN KEY (customerID) REFERENCES customers(customerID) Starting with the first operation: Foreign Key on Create Table The customerID column from the customers’ table is the Primary Key and the customerID column from the courses table is the Foreign Key of that table. Now, if you observe, the customerID column in the courses table refers to the customerID column in the customers’ table. To understand the various operations present on Foreign key, consider the following two tables: Customer Table: CustomerID Now that you know what are the rules of a foreign key, next in this article on Foreign key SQL, let us see the operations of the foreign key. ![]() The relationship established between the tables is known as referential integrity. ![]()
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