I am a newbie in MySQL and I am extremely confused about one thing. I am currently creating four tables. There's a primary key I have specified for the first table which is a foriegn key in the second table. Now the problem is that I want the same primary key to be the foriegn key in the third table as well. Whenever I am writing the query, I am getting existing constraint error. So my basic question is, can the same primary key of one table be foriegn key in three table or more? If yes, what would be the difference in the format of writing the query?