Why do we need to use Foreign Keys?
foreign-keys, mysql, primary-key, sql
Solution
When you use foreign keys you get:
- Data integrity
- faster queries.
users: user id:
- 1
- 2
- 3
Comments: user:
- 1
- 2
- 4 XXX invalid as 4 isn't in the users table.
Read Wikipedia please for more details about Data integrity
Problem
Possible Duplicate: Should I use foreign keys? Ok, let's assume we have two tables, `users` and `comments`. In comments we have a column `comment_made_by_user_id` and it means which user typed that particular comment. Why do we need to specify it as a foreign key? If we don't do that, it will still work. We specify primary keys, because it makes queries faster as far as I know (we need to search only for one row while when we don't have a primary key/index, we have to go through all rows). Is it just a good coding practise?