By using Foriegn key in a table you can maintain some relation between the two table in the database.
In other words you can also say that, a foreign key in one table allow a point primary key in an another table.
create table table_name (coloumn1 datatype(size) constraints type), coloumn2 datatype(size), coloumn3 datatype(size), ........ coloumnn datatype(size));Example:
create table employee (E_ID number(5) unique, E_NAME varchar2(20), E_SALARY number(10));Note:
Following error messages appear"unique constraints scott sys-avoided" When you avoid the Unique constraints.