How does foreign key work in Oracle?
How does foreign key work in Oracle?
A foreign key is a way to enforce referential integrity within your Oracle database. A foreign key means that values in one table must also appear in another table. The referenced table is called the parent table while the table with the foreign key is called the child table.
How do I create a foreign key constraint in Oracle?
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.
What is a foreign key example?
In simpler words, a foreign key is a set of attributes that references a candidate key. For example, a table called TEAM may have an attribute, MEMBER_NAME, which is a foreign key referencing a candidate key, PERSON_NAME, in the PERSON table.
What is foreign key and how do you use it?
A foreign key is a key used to link two tables together. This is sometimes also called as a referencing key. A Foreign Key is a column or a combination of columns whose values match a Primary Key in a different table.
Why foreign keys are used?
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.
What is the benefit of foreign key?
The FOREIGN KEY constraint is crucial to relational database design. It lets us link the data according to our needs. As it creates some dependencies between the columns of primary and foreign tables, it also lets us decide what to do ON UPDATE and ON DELETE actions performed on the rows of the primary table.
Can a primary key be a foreign key in the same table?
If you mean “can foreign key ‘refer’ to a primary key in the same table?”, the answer is a firm yes as some replied.
Is foreign key can be NULL?
Foreign keys allow key values that are all NULL , even if there are no matching PRIMARY or UNIQUE keys.