Can a relation have multiple foreign keys?
A table may have multiple foreign keys, and each foreign key can have a different parent table. Therefore, cascading relationships between tables can be established using foreign keys. A foreign key is defined as an attribute or set of attributes in a relation whose values match a primary key in another relation.
How do you create a relationship to a foreign key constraint?
Using SQL Server Management Studio
- In Object Explorer, right-click the table that will be on the foreign-key side of the relationship and click Design.
- From the Table Designer menu, click Relationships.
- In the Foreign-key Relationships dialog box, click Add.
- Click the relationship in the Selected Relationship list.
How to create a foreign key relationship in SQL Server?
Create a foreign key relationship in Table Designer Using SQL Server Management Studio In Object Explorer, right-click the table that will be on the foreign-key side of the relationship and click Design .
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 create FOREIGN KEY constraint on ALTER TABLE?
SQL FOREIGN KEY on ALTER TABLE. To create a FOREIGN KEY constraint on the “PersonID” column when the “Orders” table is already created, use the following SQL: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE Orders ADD FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);
Can a foreign key reference reference another table?
FOREIGN KEY constraints can reference only tables within the same database on the same server. Cross-database referential integrity must be implemented through triggers. For more information, see CREATE TRIGGER. FOREIGN KEY constraints can reference another column in the same table, and is referred to as a self-reference.