Question

I am trying to create this table in my php file:

mysql_query("CREATE TABLE Orders (orderID INT(3) NOT NULL PRIMARY KEY AUTO_INCREMENT,
                                  FOREIGN KEY (userID) REFERENCES Users (userID))");

However, whenever this query runs it doesn’t create the table.

Am I creating the foreign key wrong?

Answer 1

Echo result of mysql_error() after the query and you will see why the query is failing.

mysql_query("CREATE TABLE Orders (
    orderID INT(3) NOT NULL PRIMARY KEY AUTO_INCREMENT,
    FOREIGN KEY (userID) REFERENCES Users (userID)
 )") or die(mysql_error());

In your case, there is no column userID, and you are trying to create a foreign key on that column. You have to define the column first. Make sure it has exact the same data type as in Users table

mysql_query("CREATE TABLE Orders (
    orderID INT(3) NOT NULL PRIMARY KEY AUTO_INCREMENT,
    userID INT,
    FOREIGN KEY (userID) REFERENCES Users (userID)
 )") or die(mysql_error());