Oracle foreign key references

How do I create a foreign key in Oracle? Is it okay to use a non-id column for foreign key reference? A foreign key is a way to enforce referential integrity within your Oracle database. The referenced table is called the parent table while the table with the foreign key is called the child table. The foreign key in the child table will generally reference a primary key in the parent table.

FOREIGN KEY (group_id) REFERENCES supplier_groups(group_id) This clause defines the group_id column in the suppliers table as a foreign key that references to the group_id column of the supplier_groups table. This way, the constraint is enforced by Oracle. MySQL supports foreign key references between one column and another within a table.

A column cannot have a foreign key reference to itself. In these cases, a “ child table record ” refers to a dependent record within the same table. This will travel the hierarchy of foreign keys for a given table and column and return columns from child and grandchil and all descendant tables. It uses sub-queries to add r_table_name and r_column_name to user_constraints, and then uses them to connect rows. How to find tables having foreign key to a table.

If it has it a foreign key it has a reference to another table. Sometimes, it is referred as a reference key. The table in which foreign key is created is called child table.

And the table to which it references is called a parent table. SQL FOREIGN KEY Constraint. A FOREIGN KEY is a key used to link two tables together. The referential integrity, foreign key constraint, identifies a column of a table or view as the foreign key.

This foreign key column establishes a direct relationship with a primary key or unique key column (referenced key ) usually in another table. It’s used to relate data in two tables and improve the integrity of your data. There are two ways to create a foreign key on a table in Oracle: the inline method and the out-of-line method. I’ve documented them both in my guide to the CREATE TABLE statement here and I’ll explain them in this article for you.

Foreign Key Constraints. As an example, take the case of two tables, ITEM and PART. These tables have a relationship (an item can have none, one or many parts).

R_TABLE_NAME holds primary table name. If you select foreign key , grid under list of constraints holds list of foreign key columns. Another way to see foreign keys i with table designer. To open designer select table, right click and choose Edit.

To be able to do so, I had to identify the tables which could have rows referencing that redundant SYSTEMS_CONFIGURATION table. Using this definition,. The add foreign key function lists all of the columns of the table and allows the user to choose one or more columns to add to the foreign key for the table.

So maintaining integrity will not be possible. Yes you can create two foreign keys on one column which can refer two different primary keys. This is called a cascade delete in Oracle.