All I could answer is
Foreign key is primary key of another table.
Foreign key-primary key defines a relational join and relational join is nothing but merging attributes from two or more tables.
But then the next question was we can perform join on two tables and we do not require foreign keys to join tables. So what is main reason for having foreign keys. The interviewer also said that we can have a table structure without foreign keys. EDS has it's databse with no foregin keys.
Can somebody give me tell me the exact purpose of foregin key other than what I know?