How do I create a foreign key reference table?

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.

How do I add a foreign key constraint in Oracle after creating table?

After naming your constraint, add the words FOREIGN KEY to specify that it is a foreign key constraint. Then, open brackets and add in the name of the column in this table that will be the foreign key. Then, close the brackets. Next, add the word REFERENCES , then the name of the other table you’re referring to.

Can a foreign key reference a table?

InnoDB permits a foreign key to reference any index column or group of columns. However, in the referenced table, there must be an index where the referenced columns are the first columns in the same order.

Can you create a table with only foreign keys?

There is no problem having a table that consists of foreign keys only. In your particular example it would be OK to remove the OrderID. Relational theory states that each table should have a candidate key so, ideally, the business rule you mention would be in place to make the foreign key only table a “good” table.

How can I add foreign key values to a table in SQL Server?

Inserting data into tables with referential constraints

Each non-null value you insert into a foreign key column must be equal to some value in the corresponding parent key of the parent table.
If any column in the foreign key is null, the entire foreign key is considered null.

Can we create foreign key without primary key in Oracle?

A FOREIGN KEY constraint does not have to be linked only to a PRIMARY KEY constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table. So in your case if you make AnotherID unique, it will be allowed.

Can a foreign key reference multiple tables?

The FOREIGN KEY constraint is a key used to link two tables together.