Can foreign key reference multiple tables?

Can foreign key reference multiple tables?

A Foreign Key is a database key that is used to link two tables together. The FOREIGN KEY constraint differs from the PRIMARY KEY constraint in that, you can create only one PRIMARY KEY per each table, with the ability to create multiple FOREIGN KEY constraints in each table by referencing multiple parent table.

How can a foreign key connect two tables?

Using SQL Server Management Studio

1. In Object Explorer, right-click the table that will be on the foreign-key side of the relationship and click Design.
2. From the Table Designer menu, click Relationships.
3. In the Foreign-key Relationships dialog box, click Add.
4. Click the relationship in the Selected Relationship list.

Which is an example of a foreign key in MySQL?

A foreign key is a column or group of columns in a table that links to a column or group of columns in another table. The foreign key places constraints on data in the related tables, which allows MySQL to maintain referential integrity. Let’s take a look at the following customersand orderstables from the sample database.

Can a table have two foreign key columns?

(One of them referenced two others, one at a time.) So, the referencing table had two foreign key columns, and also it had a constraint to guarantee that exactly one table (not both, not neither) was referenced by a single row. CREATE TABLE dbo.

How to drop a FOREIGN KEY constraint in MySQL?

The values in the categoryId column of the rows with categoryId 2 in the products table were automatically set to NULL due to the ON DELETE SET NULL action. To drop a foreign key constraint, you use the ALTER TABLE statement: First, specify the name of the table from which you want to drop the foreign key after the ALTER TABLE keywords.

Can a child table have more than one foreign key?

Typically, the foreign key columns of the child table often refer to the primary key columns of the parent table. A table can have more than one foreign key where each foreign key references to a primary key of the different parent tables.